Improvised Weapons

So yesterday I was walking out from our local market after shopping. I rested the cart against my truck and loaded two bags of groceries and a case of Beer in the back.
As I turned around to return the shopping cart, one of my smart-ass friends jumped me from behind the next car, taking me completely by surprise. I had already reached into my pocket and unlocked my truck to put my laptop computer inside, and I was holding the keys in my left hand.
As he jumped me, I was indeed startled. But instead of backing away from the sudden attack I drove my fist holding the key like a push-dagger up into the attackers right cheek. I instantly recognized him and halted the key strike just short of punching it through his cheek. We both stopped and laughed our asses off.
I learned quite a lot in that little exchange. The posture and technique I used was the Xingyi Drilling Fist, with the key just as a push-dagger. I moved forward into the attack at an angle slightly off centerline, so it wasn't force against force. All of this happened before I completely realized who it was attacking me. My friend thanked me for not punching the key through his face, and it was all good.
After years and years of martial training, both partner work and solo meditative form practice, this kind of reaction comes very naturally and it even surprised me a bit how quickly it all happened.
I'll leave you with a little about my favorite improvised weapon, I carry these everywhere I go.

It's a simple carpenters pencil. They are twice as thick as a regular pencil and squarish in shape. Great for digging into vital spots on an attackers body. You can carry one anywhere. I don't even sharpen mine, just leave it with the ends blunt. One of the best resources for pocket-stick self-defense techniques is Masaaki Hatsumi's "Stick Fighting".
Here's a review of the book from February '08.