Being John Malkovich is a phenomenal, trippy movie to watch while high. It has it's funny moments but it mostly just crazy and awesome.
Also I totally agree with Smiley Face. It's all kinds of hilarious.
Any of the Saw movies are fun to watch baked because they're so gorey that they almost can't be taken seriously. I've watched a bunch of them with my friends while high, and it's more amusing than anything, if you're a horror-lover like me.