I want key my coworkers car.
Why would you want to damage your co-worker's car?
I don't know, I just really feel like I want to.
You should not damage other peoples' property, no matter how mush you want to, or how much you don't like them. You could get in trouble at your job and they could even press charges. It would be immature and unprofessional to do that to your co-worker.
It'll be fun to talk to my boss about it. He'll be very understanding.
I don't think he'll be very understanding of you damaging another coworkers car. You ought to try and get these types of destructive urges under control.