Create a text file on your desktop with the following line...
taskkill /F /IM hl2.exe
Now rename it "KillHL2.bat"... Or whatever name you wish to call it, as long as it has the .bat extension.
Now double click this to close Goldeneye Source (hl2.exe). Saves you going into processes.
Also, you could do what I have done and place this somewhere else, I have this bat file in my Goldeneye Source folder, you can create a shortcut for the desktop, then go to properties for the shortcut and change icon to Half Life 2 icon, saves you having that ugly batch icon on your desktop.