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1.
Gratuitous violence is violence for the sake of being violent. Usually assocciated with low budget movies and cult videogames. Given without need, often unrealistic.
Grand Theft Auto had a Gratuitous violence bonus.
by Kung-Fu Jesus April 17, 2004
 
2.
Fighting over how much to tip the waiter/waitress. Also fighting between servers over the tip itself.
"Lunch went well, except for the decision on how much to tip, which erupted into gratuitous violence."
by onasphere August 15, 2009