This is a much more difficult question than it appears. The horror genre is overflowing with quirky and enjoyable titles, to the point where making any sort of list is going to come down to personal preference more than anything else. My own list leaves off the Universal Classics (which are awesome but fairly tame), pure comedy (Young Frankenstein I adore, but going for more chills here), and the Italian gut munchers (since, in my own personal view, gore is just disgusting, not scary).
Horror of Dracula
Return of the Living Dead
Dog Soldiers
Warlock
The Thing
In The Mouth of Madness
House
Demon Knight
Kolchak: The Night Stalker (series)
I'll probably list more later, but those are likely the movies which will play well to a party environment. Dog Soliders in particular should have people going crazy.