Bloody Mess

Bloody Mess is a Fallout, Fallout 2 and Fallout Tactics trait, as well as a Fallout 3 perk.

Fallout, Fallout 2 and Fallout Tactics
"By some strange twist of fate, people around you die violently. You always see the worst way a person can die." - ingame description.

This trait does not alter gameplay other than the fact that you get to see the violent death animations more often. However, it does have an effect on the ending of Fallout.

Fallout 3
As traits were completely removed from Fallout 3, Bloody Mess was changed into a perk.

"With the bloody mess perk, characters and creatures you kill will often explode into a red, gut-ridden, eyeball-strewn paste. Fun! Oh, and you'll do 5% more damage with all weapons."

Fallout 3 definition of the bloody mess perk.