I would say that this thread sovers most of the movies that have affected us.
http://www.horror.com/forum/showthread.php?t=30312
All depends on what you mean by affected us. Is this a negative effect, like scarred us for life? Or had a positive effect, like inspired us to create art, write novels and scripts, make movies of our own?
One movie that really messed with me was Hellraiser. Movies that have inspired me are more along the NotLD, zombie genre etc. Non Horror movies that have had a positive effect on me are Pay it Forward... yeah I don't really know what else.