"the most effective, caveman simple way to identify yourself..."
I'm sure that someone in the past must have posted about these things here, though I did a search and found nothing. Came across the link on another site, and I'm still laughing as I type this - I thought that CHL badges were lame. Anyway (just in case it hasn't been linked here before): Introducing the DSM (that's "Don't Shoot Me") Safety Sash.
(Personally, I'd choose the one that simply says "ARMED." It'd look great walking around at WalMart).