I'm not touching Airbender with a long stick, but Rave to the Grave sounds awesome. Birdemic and The Room are, or course, classics, and I've made all my friends watch them.
Speaking of M. Night Shyamalan, I can't convince my sister that The Happening is a really, really bad movie. "The trees are angry" gimmick is like something the forest hippie dude in Birdemic would come up with.