Aside from any firearm(s)....
In my reach, within my truck, at all times:
Jack handle extension (1" steel tube approx 22" long, from a floor jack)
2D MagLiteGerber Metolius
It sounds like I'm looking for trouble or just paranoid, but they stay in the truck for various, legitimate purposes. I just happen to keep them in places that are extremely easy to retrieve them from... without even leaning over a seat, or really moving from a driving position.
There are many other things that could make very effective weapons, but they're locked up in their respective storage cases.
The jack handle extension made an appearance a couple years ago, when a massive jerk-wad slammed his door into mine, while I was sitting in my truck (and I didn't have a firearm). He left a 6+ inch-long drag mark, and a dent more than 1/2" deep in the passenger door. I calmly asked him for his insurance information; to which he responded by spitting on my wife and screaming about how his truck was too big to fit in the tiny parking spot (and that's my fault?
). While my wife was calling the police, I retrieved the skullcrusher, and the d-bag ran for home. Only problem?... It was a Dodge diesel with a programmer. He stomped on it too hard, and spun the rims inside the tires while trying to get away. It popped the bead on the right rear tire. So, the police didn't have a hard time tracking him down.
I need a new signature. This one sucks.