Military weaponry and equipment
Warfare
Blood and gore
Cannibalism

Flippy starts out friendly but if exposed to anything that reminds him of his past (sharp objects, loud noises, bright lights, etc.) he will "flip out" in a psychotic rage, hence his name, and kill almost anyone around him. This state is usually accepted as Fliqpy or "Evil" Flippy.
Flippy's violent alter ego was fliqpy. He suffered trauma from seeing the deaths of those with whom he served. Since then, he has developed PTSD.