I like to watch colorful visually interesting and "cartoony" stuff that makes most people go "what the fuck this doesn't even LOOK like an anime!". Panty & Stocking is one example, and there are a ton of others:
http://www.catsuka.com/player.php?id=maruko_chan_drag_racing_in_1969 (this one clip is a goddamned must watch)
http://www.youtube.com/watch?v=gz7vuwj3AlE
http://www.youtube.com/watch?v=TCuieF9Uzgc
http://www.youtube.com/watch?v=Ta6ffOIabHY

and underrated old stuff (like genuinely underrated, not the stuff that anyone who cares at all about old anime will inevitably watch):
http://www.youtube.com/watch?v=0Mtt62WIoHI (1971 movie that Hayao Miyazaki had a lot to do with)
http://www.youtube.com/watch?v=0I3IG848-dk (1963, aged ridiculously well)