It's called REISUB (one of the mnemonics is Raising Elephants Is So Utterly Boring). Press in this order and give 2-3 seconds of interval between them
Alt + SysRq + R <-- tries to get keyboard back
Alt + SysRq + E <-- term signal
Alt + SysRq + I <-- kill signal
Alt + SysRq + S <-- synchronizes filesystems
Alt + SysRq + U <-- unmount and mounts filesystems in read-only mode
Alt + SysRq + B <-- reboot

SysRq is the Print screen button (in some laptops you may need to press Fn at the same time)

This will give you a safe reboot. You can use Alt + SysRq + O in the end for shutdown instead of reboot.

Edit: upps, I'm back from the time when Ctr + Alt + Del was mostly used twice to reboot windows instead of killing just an application. Ignore the post then.