Dance genre/Any music genre that makes you copy on screen input: Reason being I suck at them and don't play them often enough to care about the games.
MMOs: A lot of them charge a subscription. For those that don't, I just haven't got round to playing one enough to get into it. Might try SW: TOR soon though.
I don't really avoid any other genres. Even MMOs I don't really avoid, I just haven't got round to playing any yet.