I'm happiest as a GM, playing at least a few different characters, both pro and antagonist.
Speaking as an evil GM, I'm with Ciosa. Evil for the sake of Evil, cruelty because 'I'm evil, that's why!' is just bad writing, bioware. As for the characters themselves, I'll play just about anything, human, non, alien, supernatural, whatever the story calls for at the time. It helps that must of my games are fantasy or sci fi things with smut in them rather than pure porn.
Really, the only thing I don't like to play are full on 'furry' characters. A fantasy or alien race with a few animalstic features is just fine, but anything that could be classified as 'furry fandom' isn't really my cup of tea.