I always forget about these ones, so here's the thread.

* Startup Command Keys

Close Open Windows - Shift
Start from CD - C
Start from OS X - X (some machines)
Select Start Up Disk - Option
Reset PRAM - Cmd+Option+P+R
Hardcore reset - Cmd+Power key, hear buzz and 3 times chime before releasing both keys.
Start Up in Single User Mode - Cmd+S
Start Up in Verbose Mode - Cmd+V
Boot into Open Firmware - Cmd+Option+O+F
Eject CD at Startup - Hold down Mouse button

* Shutdown, Restart and Sleep Keys

Deep Sleep Cmd+Option+Eject
Shutdown, Restart, Sleep Dialog Control + Eject
Shutdown, Restart, Sleep Dialog Power key on keyboard

Thank You, I've got a hunch these will be handy.

Also worth pinning I think

Hold down T at startup - Target Disk Mode

another trick:

to eject the CD if nothing else works. Boot into Firmware mode, then type 'eject cd'

also, if you wanna eject a disk you can press F12. but people most likely already figured that out when trying to open the dashboard and holding the key too long.