killall -9 (process name)

xkill" program which will allow you to left-click on a window to kill that program's connection to the X server. Although, I have not used this in a situation where I actually needed to kill something off. Anyone find this program is worth using, maybe by binding a shortcut key to it?

X won't accept keystrokes) you have REISUB;

   Alt+SysRq+R: Reset keyboard to the default input mode (i.e. take control away from X)
   Alt+SysRq+E: Send SIGTERM to all processes
   Alt+SysRq+I: Send SIGKILL to all processes
   Alt+SysRq+S: Sync (flush filesystem buffers to disk)
   Alt+SysRq+U: Unmount filesystems and remount read-only
   Alt+SysRq+B: Reboot

You could also use Alt+SysRq+K to kill everything on the current virtual console... typically this means init will respawn whatever process was running on that console to begin with, e.g. your display manager or just the text login.