That's a tough one. I usually don't like watching a movie more than once because I feel I am wasting my time when there are so many movies (or series, or documentaries) to see that I haven't.
Maybe I'd go for comedies, at least those funny enough to laugh again and again. But they are scarce. I'd go for the 10 seasons of the series "Friends", which I actually watched twice (a rare exception).
The problem with comedies is that my sense of humour evolves, and what I laughed at 10 years ago might not make me laugh now or vice versa. But that is also true for other movies. My tastes evolve. So no answer.