What I am torn between playing is: Warrior/Guardian and race Human/Charr.
Mesmer, Necro, Thief, are gonna be the last ones I'll play, If I ever will. Same goes for Asura and Sylvari.
What I also like, and am not sure about is Elementalist, too cool, but no idea about actual effectiveness.
What I find appealing but not as much as Elementalist is Engineer, the idea of random stuff just makes me excited, as I am a goblin engineer in 5 chars in wow and I love the random O-shit buttons that u dont know what to expect. Surprising both you and the enemy!
If a ranger has though, an easier time beating mesmers, it might be my choice.
I would hate playing a class having trouble against mesmer, I could work my way around other classes, but mesmer I wont really bother, so if a proffesion has even a slight (say 5%) more chance on beating a mersmer, than say, the class I will play on release, I will reroll.