Have you ever had the Dock in OS X to freeze up? Did you know you can restart it by using a simple terminal command?
Just go to the terminal app and type in killall -KILL Dock at the prompt. The dock will disappear and reappear in a couple of seconds.

I also did a quick search on Google to also find a couple commands you can do in terminal to restart finder, spaces and if the menubar becomes unresponsive.

Restart Finder

killall -KILL Finder

Restart Spaces
killall -KILL Dock

Restart  The menubar 
killall -KILL SystemUIServer