I've always like onomatopoetic words and comics just happen to be filled with them. These come mostly from 1960s Marvel comics. Some people probably only think of the campy BIFF, BAM, POW from the Batman TV show, and I know Alan Moore went out of his way to avoid the use of any sound effects in V for Vendetta (not even to show that a phone is ringing), but I think there is a certain wonderful art in coming up with these words. Fzoosh. Zeept. Krrruntch (which is so much better than a mere "crunch").