Upon close examination the F12 key has a power symbol and the letters "PC" in the yellow "function" text. However it's right next to the F11 key (duh) with the "volume up" alternate function key.
I had never noticed that before, so when i tried to hit FN-F11 to turn the volume up a little earlier and apparently missed i was very surprised when my monitor went black.
After a second or so of confusion i tried powering my monitor on and off, but it just said "no signal." Upon peering a little closer at my keyboard and seeing the power symbol i figured i'd either turned off my computer or put it into sleep mode. So i tried wiggling the mouse. No effect. Then FN-F11 again. No effect. Ctrl-Alt-Del. No effect. Several other key combinations. No effect.
So at that point i figured i'd managed to turn it off. So i pressed the power button. No effect. Then i pressed the other power button (no, i don't know why my computer seems to have two power buttons.) No effect. At this point i noticed there was a light on the front of the computer that was coming on for about a second every couple of seconds, along with a slight whirring noise. I was a little worried at this point, so i tried holding down the power button to reset it. No effect. Holding down the other power button. No effect.
At this point i wasn't sure if i should be worried or amused. So i tired turning off the power strip and waiting five or ten seconds before turning it back on. The power buttons _still_ didn't work and the (slowly) flashing light and whirring was _still_ going on. So finally i yanked the power cable out of the back of the computer and waited for 20-30 seconds before plugging it back in.
FINALLY! I pressed the power button and the regular boot up noises started and the monitor came on! After waiting a bit for that to finish i found that my previous session was still going!
So i've got a button that apparently puts my computer in magic coma mode that's impossible to wake up out of without unplugging the whole thing =P