Predator - Awesome action classic. It has Schwarzenegger, suspense, one-liners, lots of sleeveless vests and big guns. Also, the coolest alien of all time.
Predator 2 - Not so good as the original (no Arnie) but still pretty good. Some fans of the original movie don't like it at all, but it still has suspense, lots of action and I think Danny Glover fits into the role of a somewhat kick-ass L.A. cop (shame that they didn't get Wesley Snipes for the role).