For sure. I've already expressed my love for western movies some time ago so I won't repeat myself, but the Dollar trilogy is a classic and a must see for everyone. I also recommend Unforgiven, The Wild Bunch, Rio Bravo, The Treasure of the Sierra Madre, The Searchers, The Magnificent Seven and Once Upon a Time In The West of course. Basically anything that has Clint Eastwood, John Wayne or Charles Bronson in it is going to be a great watch.
There was actually a guy from my school who didn't saw The Godfather. When everyone find out, they were looking at him as if he just said that he licked some old hobo's balls.
Fuck everything else, just watch this. Now. Right now.