If I'm playing 2e (these days that only happens if I decide to play a computer game like Baldur's Gate) then I play a half-elf. Since 3e has come out I've exclusively played humans.
In the past year, I've played a human twice, but also a gnome, goblin and dwarf. I like the little guys, especially the goblins, but most GMs don't have the same "vision" of them as I do. Gotta love Birthright.
Most of the time I run games but when I play I will almost always play a human. I think that the reason I do that is because I know I can play a human rather well. Sometimes it is difficult to play one of the other races correctly but every once in awhile I will try out something different. Though I have never played anything other than the standard D&D Player races.