Okay, I'm insane, I know that. But I have this strange urge to nominate The Adventures of Buckaroo Banzai in this category. I'm not sure I can explain why. Perhaps it's just to be perverse. ;) There's just something about the character that rings true. He's a famous superhero, but he doesn't wear a costume or come from another planet. He's a mad scientist, but he doesn't cackle or plot or soliloquize. He's an odd guy…
Having John Lithgow, Jeff Goldblum, and Christopher Lloyd in secondary roles was amazing; they really go all out to push the intentional corniness over the top. (Lithgow's intentionally bad fake Italian accent is wonderful; Lloyd, as usual, really does seem like someone not of Earth; and I still don't understand why Jeff Goldblum spends most of the movie dressed like a cowboy from a 1940s serial.)
Having so much great acting around him made watching Peter Weller kind of painful to watch.