Compulsive Maniacal Laughter (3.5e Flaw)
From D&D Wiki
 Compulsive Maniacal Laughter [Flaw Types (General)]
Your character is so ridiculously evil that they can't help but gloat.
Prerequisite: Character must be of Evil Alignment and have a Charisma of at least 10
Effect: Every time something the player or the DM deems to be evil is performed by the character with this flaw, they must roll a will save DC 10+Character Level. If they fail, the character Laughs at the top of his voice, completely ruining any chances of hiding his evil nature. Intimidate receives a +3 bonus.
Benefit: Bonus Feat, +3 to intimidate if the save is failed.
Roleplaying Ideas: Salvador, an Evil Sorcerer, has just plotted to capture another character. He proceeds to laugh at his own evil nature, exposing himself to the target. -->