Requesting app: Worldcraft Editor (aka Valve Hammer Editor)
Im not sure about the other people here but I would really like to have a level editor for the goldsrc and source engines. The official editor seems to store all settings in inf files and boots fine, you can find 3.4 and 3.5beta online very easily (run from usb drive no problem) however it needs some game files/paths to run correctly. We probably just need some basic textures for it to run, I dont have time to mess with it right now. Maybe someone can check it out. The other alternative is GTKradiant.
EDIT: I forgot to mention that people who buy HL2 or Counterstrike get a SDK and the entire sourcecode for the game.