My CG Silverbrow human bard called out our party's paladin for torturing a kobold. Before then he'd been violating his code of conduct repeatedly without repercussions, and the other characters were chaotic and/or neutral, and in most cases supported the paladin's cruel actions. When he refused to comply with my demands to cease torturing the kobold, I ran deeper into the dungeon, calling out to the kobolds (in draconic) that we were sure were deeper inside, warning them that an evil, fearsome force was coming to get them.
My bard wasn't terribly intelligent, and I enjoyed repeatedly calling out the paladin on his clearly unjust methods. Anyway, I startled the party so much with my actions (I'd convinced them that the caverns were likely full of kobolds), that they chased my bard down and beat him unconscious. The bard left the party and I handed the character sheet over to the DM and told him I created an excellent background for a future BBEG.
Then I brought in a LN necromancer and showed the party what a real evil character was like. Too bad the game didn't last much longer beyond that point, as I'd just started to really enjoy the reversal of roles -- the paladin, whom I could never definitively prove was violating his code of conduct, now had to deal with my character expertly defending his outlandishly evil actions with superior intelligence.
Yeah, that was pretty damned cool.