#40 Zelda's Axiom: Whenever somebody tells you about "the five ancient talismans" or "the nine legendary crystals" or whatever, you can be quite confident that Saving The World will require you to go out and find every last one of them.
#62 Thousand Year Rule: The Ancient Evil returns to savage the land every thousand years on the dot, and the last time it showed up was just about 999.9875 years ago. Despite their best efforts, heroes of the past were never able to do more than seal the Evil away again for the future to deal with (which brings up the question of just how exactly does this "sealing away" work anyway, but never mind.) The good news is that this time, the Evil will get destroyed permanently. The bad news is that you're the one who's going to have to do it.
#107 Arbor Day Rule: At some point, you're going to have to talk to a tree and do what it says.
I randomly found this list of console RPG cliches on TVtropes.com.
And then there's the good old Evil Overlord List.