[newbie] how to kill a runaway app?

[Wade]

Hi List,

I have found an occasion or two to use the 'Ctrl, Alt, Backspace'
command a couple of times which has been a saving grace, but I have only
had a need to kill a runaway (unresponsive) app, rather than my xserver.
My question, is there a way to kill an app and not restart my xserver?
Also would this apply to a runaway process as well? 

Thanks,

b/web
Wade