I would say any of the mindfuck movies are a good choice... like Donnie Darko, Existenz, Run Lola Run, The Game, Adaptation, etc. But truely the best movie I've ever watched while tripping was The Incredibles, and no it wasn't my first time seeing it that time. It was so amazing, and I have a newfound appreciation of Pixar Studios.
Existenz is a close second though... there's something about that movie that makes me think it was designed specifically for us trippers, because I've seen it while tripping about 30 times, and it always is a different movie. I mean it. I'm thoroughly convinced that somehow Cronenburg is physically re-filming the movie and switching out my DVD before every new time I watch it. It's a crazy flick.
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