xkill
no dropping to console, just install it (if not already), select it from your "start"-like menu and click on the window for the program you want killed. You can also use a graphic task manager just like the one in Windows (ok, maybe not the exact layout but same function).
Though you do bring an interesting idea to mind. Xwindows (the service/hardware part) and the KDE/Gnome/Unity (Window manager + stuff) are separate components. Imagine being able to set your preferred game *as* your default window manager; no KDE or Gnome squeezed in between the game your playing and your hardware. Crtl+Alt+Backspace would drop you back out of a frozen game tickity-boo like it already does for any other DE running on top of Xwindows (or similar graphic UI core). Bonus points if I can alt-F2, alt-F3 between the game terminal and a full DE in the other terminals.
I'd be happy just to have my games fullscreen on top of KDE/Gnome/Whatever though personally; keep all my other stuff going in the background during games not new enough to demand premium dedicated performance.
I can't see anything in the platform that hinders the ability to do such a specialized game focuses distribution though. The existing SuperGamer or linuX-Gamer's DVD distros would be good candidates.
