Gee, should I play a human or an elf? I just can't decide! Ooh, I know! I'll play a human with infravision. I want to play with the human versatility and elf superpoweredness, and have no restrictions. Take out that whole commoners-hate-half-breeds thing! I want to play a half-elf fighter/mage/thief! (unless you'll let me play a half-drow fighter/mage/priest/thief?!)
I actually don't have a problem with any particular race, but if I had to drop one, it would be the half-elf. I feel like gnome, halflings, elves, half-orcs, and dwarves all fill cool, distinct niches. If you want to play "different," or "versatile," play human.
I started with AD&D 2nd edition and I've just seen too many players choose half-elf for what are, to me, the cheesiest reasons. I like sub-optimal builds. I think that they're more interesting. I also like narrow archetypes to follow or to flout. I don't like wishy-washy half-measures, and when the mood stirkes me, that's what I feel the half-elf is. [/RANT]