What's really fun is to play a bad character as long as you don't make a habit of this. Doug once assigned me the task of playing a lawful evil fighter-thief. My task was to get the treasure away from the party.

I was the guide to lead the party to the dungeon entrance and once there I let them "persuade" me to help out. I always seemed to hold back in the fighting and let the party absorb the damage. Then on the way out I stole the item from the person carrying it and slipped into an alcove covered by an illusion.

In our campaign all party members are expected to be of good alignment. This is yet another TV/movie rule. Good guys always win. Bad guys do not. We had a friend who wanted to sit in on a game. He brought a chaotic evil cleric. Early on he found a magic shield which turned out to be a shield of missle attraction. He couldn't get rid of it. It proved to be his death. Of course one of our dwarves took the shield and tried to use it. He played through two modules before he figured out that the shield was cursed.