The one that keeps me for getting dain bramaged. Currently that's a Giro very similar to free_pizza's above.^^^^^
I accompanied a buddy to the ER on Saturday after he stuffed himself into the trail head-first during a particularly nasty crash while landing. Helmet was toast, but he had a pretty good concussion, short-term memory of about a minute, and completely lost track of day, month (thought it was April), year, and who the President was - for about three hours. If he hadn't been wearing that helmet he'd have bought himself a trip to the operating table, not just the ER and a CAT scan.
On another note, his bike escaped unscathed.