Juice - Juice on its own is fine in a horror film, but Gin and Juice will attract Snoop Doggy Dog who will pop a cap in your mo' fuckin ass! If you've seen the film bones you will see that he ain't a pimp you wanna mess with.
Jail - If you are being hunted by a supernatural killer and the police try to keep you safe inside one of their cells, then yo ass is doomed. The killer will enter the precinct and decapitate every officer on the force before finding you trapped in a cage as if you were a birthday present.
Jack Black - The rotund comedien is useless in a horror film other than providing a rocking backing track. He couldn't help Matthew Broderick against the Cable Guy, and he can't help you.
Jeff Jarret - A disciple of the Devil, sent to corrupt our souls by televising really bad wrestling events that feature nonsensical storylines and geriatric performers.
Jupiter - If you can get to Jupiter during a horror film than you should be safe. Everyone knows that all the aliens are on Mars. Avoid Pluto however as it is full of Disney characters.
Jump - Jumping out of a window to escape bad guy = Good. Jumping across the gap between the rooftop of two buildings = Bad.