Emergency reboot with SysReq
When all else fails, before hitting the BRS, try:
Press and keep pressed both the Alt and SysReq keys
If you are using a notebook you could need to keep pressed also the Fn/2nd key
It's better to use the AltGr key, if you have it
Keeping the two (three) keys pressed, press in sequence: R E I S U B
It'll made you wish you have three hands, but it'll basically kill all the processes and sync the disks before rebooting. Hard, but way better than switching it off and on again.