I was playing the Burning Crusade at the house of a friend when I hit level 66. I went to the trainer and saw my new skills available for purchase. A deep chuckle began in my throat, quickly progressing to maniacal laughter. My friend, a warlock, looked over my shoulder to see what was so funny. He rolled his eyes when he saw what I was laughing at - I was about to purchase Cloak of Shadows. "Don't be so happy. It's going to be nerfed soon," he said. All I could say was "Then we better duel really, really fast. Ready?"
I am very happy with Cloak of Shadows, and have put it in the row of "Emergency Kill Quick Buttons" along with Berserking, Evasion, Adrenaline Rush, and every trinket that increases attack power when activated. I've also been having fun with Deadly Throw, which allows me to be a jerk to mages and hunters. Envenom is ... well, Envenom sucks.
Every class seems to have at least one really awesome new ability. Whether it's the mage's Ice Lance (most often heard being said to rogues, as in "Just wait until we have Ice Lance"), the priest's Shadow Word: Death, or the warlock's Ritual of Souls (which isn't that great but will at least stop people from opening trade for healthstones), players have something really exciting to look forward to as they ding new levels. What ability are you most looking forward to, or if you've already gotten to 70, what ability do you like the most?