Admiral Daelin Proudmoore: Father of Jaina, Derek, and Tandred Proudmoore and Finnall Goldensword. He was the ruler of the Human nation of Kul Tiras. What we know about his record as father is unfortunately not the best. Probably the best thing we can say about him is that he strove to build a safe world for his children, fighting off the Horde in the first and second wars with ability and fervor. It was only afterwards during the events of Warcraft III that things went south for him.
Instead of fighting the Scourge, he decided to sail to Kalimdor in pursuit of the Horde, believing that they would build up power on the far shores and return to wipe out humanity once and for all. He asked his illegitimate half-elf daughter, Finnall, to come with him -- perhaps a sign of his fatherly love, as he also believed Lordaeron lost to the Scourge and may have wanted her to escape with him -- but she rejected him, and accused him of running from the Scourge and the true fight for their homeland. In Theramore, he usurped his other daughter's rule and tried to use her people and resources to destroy her Horde allies, which eventually lead to his death at the hands of Rexxar.
You can play through the story of his downfall on the Orc Campaign of Warcraft III: The Frozen Throne. Despite his early heroics, poor Daelin died a broken man, opposed by his children. Finnall still considers him a coward last we knew, but perhaps Jaina and Tandred will remember their father in happier days today.
Durotan: Father of Thrall. While he did participate in some of the early attacks against the Draenei, he was one of the only Orcish chieftains who stood up against the demonic corruption that nearly consumed the Horde, refusing to drink the blood of Mannoroth. For this, he earned the wrath of Gul'dan, and his clan, the Frostwolves, were exiled to Alterac Valley, where his mate Draka gave birth to Thrall.
Inspired by Thrall's birth to confront Gul'dan and ensure a safe world for his son, Durotan traveled to the encampment of his childhood friend Orgrim Doomhammer, now Warchief of the Horde. While he was able to convince Orgrim to help him stand up against Gul'dan, some of Orgrim's guard were spies for Gul'dan. They summoned assassins who trailed Durotan and Draka as they left Orgrim's camp and killed them both.
If you're willing to face down one of the ultimate evils in the universe in order to stand up for what's right and make sure the world is a better place for your kid, that's real love, and a good example for your child. Thrall has nothing but the deepest respect and love for his father, and named the new homeland of the Orcs, Durotar, in his honor. That's a heck of a Father's Day present, if you ask me.
Nielas Aran: Father of Medivh. He was the court conjurer of the kingdom of Stormwind in the days before the Horde invaded Azeroth. Unfortunately, becoming a father sealed his doom. He was seduced by Aegwynn, Guardian of Tirisfal. She was looking to produce an heir to inherit her power, and chose him because of his innate magical prowess. Once she had her heir, she left Nielas to raise the child on his own in Stormwind. Unknown to anyone, Medivh himself was possessed by the spirit of Sargeras, which had entered his body via Aegwynn, but appeared to be a normal boy through most of his early years.
On his 14th birthday, Medivh fell into a trance and began to radiate massive amounts of energy. Nielas attempted to reach his son and contain his power, but was killed in the process. Eventually, his tormented spirit was drawn to Medivh's tower, where he wandered restlessly among the books of his son's library. Finally, a group of adventurers working for the Violet Eye found him and put him out of his suffering, sending his spirit to a well deserved rest.
Thus ends the sad tale of Nielas Aran, jilted lover, hard working single father, and tormented spirit. He deserves a big hand on Father's Day for all he went through for his son, that's for sure.
Arch-Druid Fandral Staghelm: Father of Valstann Staghelm. You can't accuse this father of not loving his son. After he lost his son in battle to the Qiraji during the War of the Shifting Sands, Staghelm fell into a deep depression from which he has never really recovered. He's defied the will of Dragons in his grief and changed the destiny of his people while questing for a way to bring him back.
The dragonflights joined the war after Valstann's defeat and death at the hands of General Rajaxx and managed to contain the Qiraji and the Silithid behind the gates of Ahn'Qiraj. The bronze dragon Anachronos set up a gong that could be rung to reopen the gates and handed the scepter which would ring the gong to Fandral Staghelm. Fandral, still possessed by grief and anger over the loss of his son, threw the sceptre to the ground, causing it to shatter into pieces, and vowed to Anachronos that he would get his son back, even if it took a millenia. We don't know for sure, but it seems very possible that one of the reasons he made Teldrassil despite the protests of the Dragons was to prolong his search for a way to recover his son by regaining his Immortality.
It seems unlikely that he's given up his quest, so I have to commend him for being a dedicated father. However, he may be taking that dedication just a tad too far, especially if some of the rumors about him usurping Malfurion's power and conducting dark experiments using Morrowgrain are true.
Grom Hellscream: Father of Garrosh Hellscream. Grom himself is probably one of the most controversial figures in all of Warcraft lore. He was one of the first chieftains to drink of the blood of Mannoroth, and drank it again in order to defeat Cenarius during the Warsong clan's invasion of Ashenvale. However, he also mentored Thrall in his rise to the station of Warchief and defeated Mannoroth, which some say ended the blood curse of the Orcs for good. In short, he is considered a villain by the Alliance, but is honored as one of the greatest heroes of the Horde.
But what of Grom as a Father? Many people would say he was a fine older brother or father-figure to Thrall, and taught him much of what he needed to properly take rulership of the Orcish clans on Azeroth. However, it's much less clear how much of a father he was to his real son, Garrosh. Garrosh himself did not partake of Mannoroth's blood, and at one point considered himself disgraced at his father's genocidal actions while under the influence of demonic corruption. However, after Thrall came to Garadar and conjured an image of Grom's final battle against Mannoroth for him, Garrosh gained a new appreciation for his father, one that perhaps even borders on worship. Of course, if you believe some of the rumors, Garrosh has also gained his father's tendency to be headstrong and hasty, and is acting recklessly and arrogantly as he leads the Horde's forces into Northrend, so it may be that Garrosh hasn't truly learned from the mistakes his father made.
Grom will probably be a controversial figure in the Warcraft universe as long as people still play the Warcraft games, and there's valid arguments on both sides for how much honor he truly deserves. However, Grom will certainly be honored on Father's Day. What remains to be seen is whether the legacy he left Garrosh and Thrall will turn out to be for weal or for woe.
Tirion Fordring: Father of Scarlet Highlord Taelan Fordring. Despite being one of the founding members of the Knights of the Silver Hand, Tirion was convicted of treason for befriending an Orc named Eitrigg and banished from his home in Hearthglen. However, he stayed in Lordaeron and hid himself in order to watch over his son Taelan, who believed him to be dead.
While Taelan grew up to be a noble and powerful member of the Silver Hand and rose to his father's former position as governor of Hearthglen and lord of Mardenholde Keep, he eventually fell. Driven to grief and despair by the death of his friends and family at the hands of the Scourge, he was seduced by the Scarlet Crusade. Tirion, however, did not give up on him, and eventually recruited an adventurer to confront Tirion with various tokens of his past, hoping to remind him of his true honor and duty. Once reminded by this adventurer, Taelan remembered his father's love, and attempted to leave Hearthglen and rejoin him. However, just as he was about to make his escape, he was killed by Isillien, the Scarlet Crusade's Grand Inquisitor. Tirion killed Isillien in turn, and vowed that Taelan's death would not be in vain, and that he would end his exile and found a new order to destroy the evils of the world.
It seems that in WoTLK, we will see the fruits of that vow, as rumors place Tirion Fordring on the shores of Northrend, ready to lead the Silver Hand against Arthas himself. Certainly, Tirion's sense of honor and justice, combined with his incredible dedication to his son's well being, makes him one of the greatest fathers of Warcraft Lore.
King Varian Wrynn: Father of Anduin Wrynn. The once and future King of Stormwind, Varian Wrynn has been an absentee father for the past few years, although not by choice. He was ambushed and captured by the Defias Brotherhood while heading to a diplomatic meeting with Jaina Proudmoore at Theramore.
After the ship wrecked, he washed up on the shores of Durotar with no memory and was captured by an Orcish shaman named Rehgar Earthfury. After fighting in many Gladiator battles for Rehgar under the name Lo'Gosh, he eventually escaped with the help of a Druid named Broll. After helping the Night Elves battle the Warsong clan in Ashenvale for a time, he was eventually sent to Jaina by Tyrande, who along with Aegwynn was able to help him regain at least a part of his memory. He is currently eager to rejoin his son in Stormwind, although there is some speculation that his time as a slave in the gladiator pits of the Horde has made him bitter and hasty.
If we can give praise to Varian for anything though, it is likely Anduin. According to the World of Warcraft manual, Anduin is "as wise a king as any 10 year old has a right to be," which suggests that Varian raised his son well. In addition, Varian left him in relatively good hands in the care of Bolvar Fordragon, who has proven to be both a powerful and wise regent -- when he's not under the control of a certain dark power. Anduin also asks almost everyone who comes to see him for news of his father, so it's likely that he thinks of him often. Hopefully, the two will have a happy reunion soon enough, although it looks like they'll have to wait until next year to celebrate Father's Day together again.
King Terenas Menethil III: Father of Arthas and Calia Menethil. As the last King of Lordaeron, he forged the Alliance alongside Anduin Lothar and helped Lothar lead it through two wars against the Horde. Unfortunately, he also lived to see that Alliance nearly fall apart, and was betrayed by his Son in the end.
There's little to say of Terenas' sad end. Despite the pleas of both Dalaran and the Prophet Medivh, he refused to act decisively to protect his people from the Scourge, either by quarantine or by flight to Kalimdor. To his credit, he did apparently try to recall Arthas' troops in the end, perhaps finally realizing that he needed to reign in his son's recklessness. However, it was too late. Arthas only returned when he was ready, and his first act upon seeing his father was to murder him and summon the Scourge to lay waste to the capital. Even in death, Arthas continued to mistreat his father, stealing his magical burial urn and discarding the ashes.
It is likely that Arthas is too consumed by evil to honor his father on this day, although if Calia Menethil is still alive, perhaps she may be honoring her father in her own way -- If she's not angry at him for trying to marry her off to a dragon.
Blackhand the Destroyer: Father of Rend, Maim, and Griselda Blackhand. Blackhand, who appears as a King in Karazhan's chess set, was the first Warchief of the Horde and essentially no more than a pawn of Gul'dan. He was also arguably not much of a father.
To start with, he denied his daughter Griselda the right to drink the blood of Mannoroth, and then sent warriors to kill her when she eloped with an Ogre name Turok and ran off to the Deadmines with him. He seems to have treated his sons better, and they stayed loyal to his memory after he was assassinated by Orgrim Doomhammer, often challenging his authority as the new Warchief.
After the Second War was over, they eventually fled to Blackrock mountain, where Maim died and Rend declared himself the new leader of the Blackrock clan and Warchief of the Horde by birthright. Following in the legacy of his father, he also became little more than a pawn of a higher power, in this case the dragon Nefarian. Eventually, he was assassinated, also like his father before him, this time on the order of Thrall. "Like father, like son" has never been more apt than in the case of the Blackhand family.
Pelturas Whitemoon: Father of Relara Whitemoon. While neither Pelturas nor Relara are major figures in Warcraft lore, it still feels like Pelturas himself deserves a mention.
Pelturas lives with his daughter in Astranaar in Ashenvale. When his daughter came down with a strange sickness that sapped her strength and left her trapped in nightmares, he began tirelessly searching for a cure for her, sending adventurers to all corners of Ashenvale for rare and dangerous ingredients while he stayed by her side and tended to her. Sure, he's not as legendary as some of the other fathers we've covered in this article, but he did his best to move heaven and earth for his daughter's sake. In the end, that's one of the best things a father can do for their children, I think, and he definitely deserves some recognition for it on Father's Day.