Items I keep on hand:
Good pair go leather Mechanix gloves. (I know a lot of guys just say gloves, but I'm a snob in this area.) Cold weather gloves would be a wise investment. Changing a flat in the dead of winter during a storm would suck with normal gloves as they soak up water.
Hand Warmers
Emergency hand crank and solar AM/FM NOAA radio with USB for charging my phone.
Tools: wrenches, pliers, star bits, torque wrench, lug wrench, demolition tool ( My "Annihilator"), folding shovel, ax, bolt cutters, tie downs, screw drivers, and bungee cords. Oh and rope. Good rope.
Telescoping fishing rod. Never know when you might need/want it.
First Aid kit, road flares, emergency spot light, water filter, fleece blanket, emergency blanket, tarp, jumper cables, one of my favorite family pictures (aka motivation for life), and some freeze dried food.
If I'm traveling in winter I'll add some sand or kitty litter along with some extra heating items. Frankly though, I'm no yuppie. The only way the cold will get me is it's faster than my hips.
Crap, better start loading up extra goods.