Thought I'd seen or at least heard of practically all the techniques years ago; then there was the fire piston, which was a completely new principle. Now this:

http://www.wmuma.com/tracker/skills/fire/cokeandchocolatebar/index.html

I'll reserve judgement until I actually try it, and it's not on the schedule for this weekend. <img src="images/graemlins/wink.gif" alt="" /> Definitely something I wouldn't have thought of, though.