Pictures speak louder than words, but here's an overview. I live in a pretty small apartment (one bedroom), so I don't have a lot of storage space. And, of course, since I just got my TM P90 recently, (and got it used off ebay) I had to put it through it's paces, test firing, etc. Well, that went fine. So, satisfied, I ejected the mag, turned on the safety, and set it down on my desk, thinking nothing of it. So several days later, I remembered I still had the battery in there, and I should probably take it out and discharge/recharge it before I used it on the field (since I'd fired a good 400 rounds during the test firing). I picked it up, and my hand slipped a little, my fumbling fingers both disengaging the safety and simultaneously firing the BB that I'd neglected to remove from the chamber straight into my computer monitor 20 feet away.
These lines are permanent now. They turn different colors if you push on them though.
Closeup. Here you can clearly see the point of impact, and a perfect impression of the BB in the screen, complete with star pattern impact lines.
Sorry for pic quality. Taken with my cameraphone.
LESSONS:
Disconnect your battery when you're not out actively playing.
Remember those BBs in the chamber (which mostly applies to the unusual guns that load from the top, like the P90.
Keep your airsoft guns away from expensive delicate things.
I'm just glad I didn't hit my 50" LCD HDTV. Which I easily could have.