Working in an office setting, some of the easiest access weapons would be pens, desk lamps, coat racks(break the base off and you got a nice bo.) Keyboards, monitors(we have flat panel), and anything you can throw. As for my vehicle, I have a bo and some escrima sticks in my truck, so it is a mute point.

car combat - always have your keys in hand, never in your pocket, that pile of pennies in your center consul might be of more use then just over pumping at the gas station, a handful of pennies in the face isn't pleasant. My instructor actually squirted me in the face with some hand-sanitizer, it was enough to get the upper hand alright. Take a look at your steering wheel and think of all the arm bar and key lock variations you can do. Seat belts can choke and rear view mirrors can be broke of pretty easy for a little hand held weapon.
My instructor also says whenever he goes into a bar or wherever, he checks to see if the chairs are bolted down or removeable, are the tables thick enough to stop bullets or big enough to hide behind, how far of a reach is it to the bottles behind the bar, do the bouncers have any visible weopons (flash lights, pepper spray, etc.), and can the windows be smashed or jumped through for a quick exit.

can wood stop bullets?

not all tables are made of wood

thats true. i don't many tables would stop a bullet.

Here's a link that I thought was really cool. Training in using a chair as a weapon. The perfect improvised weapon; it's got reach, it's solid, it can be heavy and has several pointy bits for thrusts as well as being useful for a more carefree, but satisfying "smash over the head"

Just had an idea...

I keep a bottle of Habanero hot sauce (one of the hottest chili peppers in the world) in my office desk. If time weren't an issue, mixing it w/ water to throw in the face could be nasty - liquid pepper spray.

Geeze, hedkikr, why not just throw rubbing alcohol on their face and light it up.