Anger Management (3.5e Trait)
From D&D Wiki
 Anger Management
This trait implies that your character has difficulty managing his/her anger.
Benefit: When provoked or made angry you fly into a fit of rage, much like that of a Barbarian's. During this raging period you gain Con +2 and Str +4. You also gain the Die Hard feat as a temporary bonus feat even if you do not meet the prerequisites. You may enter this state as often as it comes up.
Drawback: Entering a state of rage is NOT optional. Entry into a state of rage is decided by the DM. However DM's must remember that it takes a substantial amount of provocation to enter this state, they won't just enter it every time some one attacks them, or laughs at them. Once a state of rage is entered it will continue for 5 rounds or until whatever caused such immense rage is eliminated. While in rage, the player can only think about the destruction of whatever brought this rage upon him. Also, when you are in a state of rage these effects are being caused by massive ammounts of adrenaline being released into the system. Due to this huge burst of energy you will be fatigued for 24 hours afterwords. Also, after leaving a state of rage you must succeed on a fort save (15) or take 1d4 of non-lethal damage.
Roleplaying Ideas: A character who has this trait will exhibit other signs than just raging every so often. A character could take abuse and cruelty until it boils up and he snaps at people, mentally and maybe physically abusing them. Or perhaps the player with this trait will take out his anger immediately and physically on the provoker. How players will express this trait varies, but the main point of it is that they have trouble managing their anger.