Rocky Horror Picture Show (I estimate that I've seen it 300 times and I'm ready to go again)
Monty Python and the Holy Grail (funniest movie ever)
and
and
I CAN'T PICK A THIRD! There are many movies tied for third that I can watch over and over, but it depends on my mood and time of year. For example, I can easily watch and enjoy 24 hours of A Christmas Story each year. Brazil, Amadeus, The Exorcist, Shaun of the Dead, Willy Wonka and the Chocalate Factory, Heavy Metal. And lots more.