My favorite has always been science fiction.  The more firmly grounded the universe the better.  While I have never been a huge fan of magic, I do admit a strong affinity for Shadowrun.  BattleTech is my first love.

The classic fantasy setting is pretty low on my list of likes bit it is such a popular setting that I simply can not ignore it.  So I tend to make my own or look for settings that are low on the more bullshit elementals of fantasy.  Again, the more firmly grounded the better.

No-go zones are most things including anime, super powers and modern popular culture.