The majority of the people who play chose their main character's race because it appealed to them for one reason or another. Some people play a certain race because of the racial traits and the benefits they provide in a raid. The extra crit or intellect can be the defining choice when a raider is picking his or her race. A serious PvP player may choose his race based on the offensive or defensive racial traits for that race. For the average player, though, we choose our race because something appealed to us: the look of that race, the lore, or maybe it was the thought of how playing a certain race and class combination would play out.
My very first toon in WoW was a gnome rogue. The thought of something so small jumping out from the shadows and stabbing you in the kneecaps before vanishing made me laugh. I moved onto a dwarf hunter a few weeks later and never looked back. The dwarven race has always been my favorite because of their lore, the way they carry themselves, their attitude. When I think of dwarves, I think of Scotland and bagpipe music. In Wrath of the Lich King, I spent more time in the Howling Fjord than any other zone. If I could have taken the music from the Fjord and put it in Ironforge, my dwarf would have been drunk on ale and in heaven. Every character I have, save for my first rogue and my priest, is a dwarf.
What is your favorite race? Why does that race appeal to you? Are there any races that you can't stand to play or dislike in general?