Really surprised only one person has said Monty Python and the Holy Grail. edit: actually watching this now.
Awesome movie.
I also the following movies-
The Matrix series,
Forrest Gump,
Caddy Shack,
Tommy Boy,
The original Clash of the Titans,
One Flew Over the Cuckoo's Nest,
Dances with Wolves,
300,
Ferris Bueller's Day Off, <3
Lord of the Rings series,
Step Brothers mainly because of it's idiotic comedy and Will Farrell,
The ORIGINAL Planet of the Apes,
Ben-Hur (not sure if they made remakes, but the original is awesome),
Dude, Where's my Car? (Ashton Kutcher is fucking hilarious),
The original Conan the Barbarian,
For some reason I also sort of like the Harry Potter series,
Radio,
Jaws,
Karate Kid (with Ralph Macchio),
The Odyssey (1997),
Cba to name any others. Will come back and edit this post eventually.