My truck is pretty well equipped.  
I keep a "go" pack in there with knife, saw, rain jacket, cook set, canteen with water, water filter, tarp, survival kit, first aid kit, flashlight, etc.  
That pack carries the sort of stuff I could use to spend a night in the woods with fair comfort.
I also have a range basic supplies in my truck tool box:  hand tools, tow chain, jumper cables, fishing gear, hatchet, tie-downs, etc.
Not too long ago, I put together a small kit that I could grab quickly to render some basic emergency assistance.  Here's the kit.
		
		
	
	
Based on Moosez45's BK-3 vs. Dodge Omni video, I'd say the BK-3 is good tool to have for an emergency.
I may swap out my Camillus version (above) for the Ka-Bar version with the striker pommel.
[video=youtube;QSuZxLT8_iY]http://www.youtube.com/watch?v=QSuZxLT8_iY&feature=player_embedded[/video]
Here's all the stuff in that kit above: (from top left, first row) first aid kit, nitrile gloves, emergency poncho, couple of space blankets, (next row) safety glasses, reflective vest, Spyderco D'Allara, Surefire G2, (next row) road flares, leather gloves, paracord and duct tape, BK-3 Tac Tool, Leatherman Surge.