When that magazine has 40mm grenades on sale in all non-splody types.
Got a Streicher's right next to where I work, and while it's aimed at police and military service members, it's still nice to get some hands on with gear before you buy it. Picked up my Streamlight Protach 1L there (was looking mostly for holsters, figured if I was going to start carrying a flashlight would be handy too). Signed up for their catalog while I was at it, because it's always fun to read about things you can't buy (I've always liked tactical shields and the like, never mind that they're worth more than my present car).
Other things they have you don't see for sale elsewhere: flashbangs, those collapsible road spike strip things, evidence bags, and tactical body armor.