Here's a new one:
Desktop is being wonky. So I go to reboot it. It's locked up in the "shutting down" state so I force a reboot.
Comes back up and it's being absurdly slow. Desktop icons appear than disappear. So I force a shutdown (read: pushed and held the power button). Then I notice... it's not completely off! Something's still making noise in there. Don't know if it's a hard drive or the power supply fan or what.
Killed power to shut whatever that was off, and now we're back in business.