Helmet Fire, Good example with the Jaspers Brush accident, beat me to it!
Another accident where BASI mentioned helmet was in Qld a few years ago. 206 on charter ops autorotated into water very hard and all on board drowned. Pilot was knocked out in accident and passengers were either incapacitated or unable to exit. General comment was that if the pilot was wearing a helmet he would have been conscious after the accident and would 'probably' have exited the aircraft. He may have then been able to help the pax.
This was post accident speculation on the part of the investiagtors, but a clear message from this is the opportunity to survive was diminished because the pilot was not wearing a helmet.
My preference is to wear it when-ever possible.
Gibbo
P.S. 430 driver - If your helmet restricts peripheral vision for any ops (including SPIFR) then it is either a poor fit or a poor helmet. The only bit of the helmet you should be able to see (through) is the visor.