Short version: I was like, WTF? Kernel panic? You gotta be kiddin me!
Elaborate version: My first kernel panic on MacOS X in two years. Because it's such a rare event, I had to take a photo. A kernel panic is an operating system crash, the Mac OS X equivalent of the Windows BSOD.
It happened when I unplugged my K750i cellphone from USB (after unmounting). Shouldn't happen, and I thought Apple had fixed this in 10.4.
UPDATE: I think I know how this crash came to be. The K750i has a wide-ish system connector with lots of pins in a row. If the phone is connected to USB and you unplug it from the phone first (with the USB connector still plugged in) it's possible to pull the system connector off unevenly so that some pins are still connected to the phone and some are already off. I think this causes a hardware problem that makes the USB interface in the Mac throw up.