I have had one fire off without an igniter on it before. I had my ignitor on the plug, took it off to prime the motor on the box and it fired. Only happened once but it sure was cool.

I also watched a buddy put his ignitor on last week and it almost turned over with out a box. A loud pop. must have been just enough nitro left in the chamber from previous run.

I had a SH motor (i know what your thinking but I needed a motor quick and got it used already broke in) that sounded like it would backfire when it was cold. Never ran backwards but the smoke rings from the pipe got everyone's attention.