The little dudes
Gnomes and Halflings (the old D&D Hobbits, that is. And for that matter, the old big-nose, pointed ear gnomes). I don't know why, but they work well with me. I've always liked the reluctant-hero hobbits, and the image of the wise woodsmen with a sense of humor of the classic-style gnome. I am sometimes asked to play one of these two, on the race chance I get to be a PC.
However, my default race is Human. Basic, easy, I can role-play them, and they don't rock the boat in the race department. I've tried dwarves, and I really like the race, but I'm just not dwarfy enough. I can play them, but can not 'become' them. I don't 'do' elves and half-elves. I like it when others play as them, and play them well, they are just not for me. I've always been tempted by the half-orcs, but I have a feeling that they will not click with me.
If I could, I will occasionally deviate to non-core races. I was told I did a really good job with a kobold, a half-ogre, and a Zeetvah (sp? woo, one of my *real* favorite races, if you know SnarfQuest).