Any evil
I prefer to play some sort of evil. Usually it is Lawful Evil.
What I like to do is play a normal good person with a blind spot on something that makes him a bad guy...such as believing all elves should be burned alive...that elves are at the root of all the world's evils and by removing them we can have a perfect society. ....it's a bit Hitlerish.
but it allows me to play with the party with no problems as long as nobody plays an elf...(or whatever the blindspot is)
Typically the easiest road for me to prusue this belief system is an evil religion. Most of the time it is a religion that favors the strong over the weak...
One of my players and I have a running arguement about evil races. I'm of the opinion that they are evil because of culture and not because of nature. He wants to wipe all orcs, gnolls, drow, etc. out of existance. I find that evil since I view them as culturally evil, whereas my friend does not find it evil because he believes it is their nature to be evil. (in the case of drow or anything that breds with the lower planes, I might agree.)
I usually find myself in the position of saving the orc babies when my friend throws a fireball into the orc nursery.
who's the good guy? (his alignment is usually chaotic good or neutral good)