Some races just don't get a lot of play in my games. Here are a few.
Cat-Folk - I just don't love cat people. I like actual cats, but I don't really like cat races. Some of it is the actual racial designs, a much of it is not wanting players do all sorts of cat-themed roleplaying.
Most animal-men fall in the same disused category. The occasionally bear-man doesn't bother me too much, though.
Centaurs - I'm not a horse person, either - although I am a basashi fan. I really actually like the idea of centaurs, but they come with just so many issues - the whole horse body thing makes for a lot of issues. Can't go upstair in the inn. Can't fit in the carriage. Can't climb up the rigging on the pirate adventure. Can't, can't, can't. And what they can do isn't terribly better than what human-like beings on horses can do.
Variant centaurs have much of the same issue - wemics, for example, or any other quadruped-with-a-human-body types. Vrusk were exceptionally cool but came with issues in Star Frontiers in a way none of the other races were.
Pixies - and sprites, brownies, and other tiny flying races. Generally the issues is the annoyance of scale. I find them difficult to play as a GM without them being annoying instead of fun. As a GM, I tend to nix them from the list faster than you can say, "Hey, everything in the game has a penalty to hit me, right?"
What races don't really see much use in your games?