On my person I have a Leatherman Wingman.  There's hardly a day that goes by that I don't use it for something.
I also carry a SOG Flash II Tanto, but to be honest, I hardly use it.   I love the knife, but the first thing I always end up grabbing is that Leatherman.
I also carry a WaterProof Butane Lighter.  I just like the idea of being able to create a little flame anytime I need to.
My car kit is much more extensive.   I don't keep a jump starter in the truck.  You'll destroy them if you let them discharge, which they naturally do over time.   I was told to top it off every 30 days.  I know I just wouldn't remember anyway.
I have a 12v Portable inflator, a 12v Impact Wrench, Duct Tape, some Datrex Water, some Energy Bars, some of those LED Road Flares, some Chemical Light Sticks, flashlight, Jumper Cables, First Aid kit etc...
I have more gear in my EDC Backpack that I take to work and pretty much everywhere else.  Flashlight, Multi-Bit Screwdriver (which gets borrowed at least once a week at work), a small LED flashlight, First Aid Kit, Sanitizing spray and some other goodies..