Knowing that it is never too late to become hideously disfigured in a car accident, explosion, etc. is a terrifying thought.
Shitting blood is fucking scary.
Going crazy and knowing it, but not being able to do anything about it.
Being involved in a mass shooting.
Being wrongfully imprisoned.
Any sort of accident leaving me in a vegetative state in which I want nothing more than death, but am unable to say "Just pull the plug", and am therefor kept alive for absolutely no fucking reason.
But mainly SNAKES.