The worst wipeout we have ever seen has to be on this left by Albee Layer. The cringing and teeth sucking starts at around 0.54 mins and continues in slow motion until 1.13 mins. The sadistic part of me wants to watch it over and over again.
Don't bother watching the rest of the movie as he makes most of the other waves and I am sure you don't want to see the very nearly completed 720 and 540 attempts along with some thick barrels and a very classy 'shimmy' at 2.22 mins.
Albee Layer moments before destruction.