Can't really say what counts as old these days, but I would recommend, without a shed of irony, the first Die Hard as it's one of the most psychotic action flicks ever made. (And Christmas movie, because it counts dammit!)
Others would include: Apocalypse Now, for being a unique adaptation of Joseph Conrad's Heart of Darkness.
Pulp Fiction, because Tarantino is always in season, and finally ...
Xtro: the best B-movie ever made. We're talking toy soldiers coming to life, extraterrestrial abductions, and a kid with telepathic abilities.