12 Angry Men (1957)
Probably the best low-budget film I've ever seen. Entire movie takes place in a single room, and the writing carries the whole story.
The Thing (1982)
well written horror film, with amazing practical effects from the time, that still hold up today.
Point Break
Absolute classic, a dated, but must watch for cultural enlightmentment
Terminator 2
Terminator 1 was kinda ok, but Terminator 2 is classic 80s film and just kinda great.
Star Wars (episode 4-6)
You've seen this film, and on the 1% chance you haven't, don't watch it. Go watch Firefly instead, that's a much better thing to watch. Also if you haven't seen it and you DO want to see it, watch the despecialized edition of episode 4 at the very least.
Top Gun
An accidentally, incredibly homo-erotic film that has aged terribly, the only good part of the whole damn film was "Lead Me On" and "Danger Zone". The Flying scenes were decent, and I know it was 86 when they filmed it, but there's literally no other substance in the film, other than some of the crazy shots they do to make Tom Cruise not look tiny next to the big boys.
Back To the Future Parts 1-3
These films speak for themselves, if you haven't seen them, please do.
Fight Club
Great Mindfuck film, a must watch.
V for Vendetta
INCREDIBLY relavent film to watch today. My personal favorite film as well.
Hot Fuzz
Great Britian comedy film that does more than just deliver dry lines as ""comedy"" and call it a day.