Splinter
Three people trapped in a remote gas station while a deadly fungus tries to get inside to infect them.
Right At Your Door
A dirty bomb goes off in LA, a man traps himself inside his house with a stranger while his wife is stuck outside.
Evil Dead 2
A spooky cabin in the middle of nowhere. It doesn't get much simpler than that.
Night of the Living Dead
Nothing like trying to survive the zombie apocalypse by sequestering yourself in a farmhouse.
Feast
A group of people trapped in a bar while monsters try to get in.
I'm sure I missed some, so what other movies manage to do a lot with a single location?