It's a boring answer, but there isn't a class I don't like playing. I think I've played them all into hero range at some point or another. I even enjoy healer in the right circumstances.

Race-wise, I tend to play the half-races the least. I'm not so much about moderation, so if I'm taking an XP penalty I tend to want it to be a big one. I don't tend to play svirf or gnome either, despite imming one -- when I do I get frustrated pretty fast typically.