Deadly Strength (3.5e Flaw)
From D&D Wiki
It is suggested, young warrior, to just keep your hands in your pockets and don't touch anything.
No matter what your character's intentions are, your attacks always cause lethal damage... even with your fists.
Effect: You may not chose to deal nonlethal damage. Attacks you make with weapons that cause nonlethal damage, including unarmed strikes, must be made to deal lethal damage instead. If you attack a creature you must make it lethal. When handling fragile things you must role 1D20 +strength bonus and if you get more then 10 you break it. Less then 10 you don't break it. You must do this every time you handle a fragile object.