There are a bunch of different versions of the gas/water shut off wrench, Sears has one for $10.99 online.

I posted a picture of the version I bought 2 of, but it looks like it was removed (I may have broken a rule), had a "hammer" and pry bar feature that seemed kinda useless, but I have shut off water and gas with the wrench I own.

The tool above looks scary, eh? Conan style....