I keep a Leatherman Supertool in the glove box, a seat belt cutter ($1.50) in the sun visor, and a 15" crowbar (Estwing -- very light!) by my seat.
Crowbar may help in the unlikely event of an accident. And in the even less likely event of car-jacking, well ...
BTW, Blilious -- are you asking primarily RE emergency or protection?
Glen
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Thank me -- my posts make yours sound smarter.