Like the bass bombs, it's definitely one of those things you'd want to use sparingly though. It doesn't take long to get stale if you use it in every tune.
Something else I kind of like doing, using the same effect, is to do the reverse reverb thing, but with about a 3 or 4 second trail. I've then applied a kind of stereo chorus/flanger/phaser to it. Seems to work well in a transition from, say, an intricate acoustic intro into full blown thrash. As the verb gets more intense, with the swirlyness of the flanger, it kinda has a similar effect to a fighter jet flying over, stopping dead with the first chord of the heavy part.
), but it makes a lot more sense if you listen to the track. It's pretty similar to the stuff Zep was doing back when. 
