I just saw a kinda neat rachet at Advance Auto a couple of weeks ago. It worked with 1/4, 3/8, and 1/2 inch sockets, so it would eliminate the need to carry 3 separate rachets in your emergency kit. It isn't something you might want to use in your garage, but on the road it might come in handy.

I don't know if anyone mentioned it yet, but those spare tire inflators/sealers in a can are good to carry with you too.

Don