Best Looking Graphics Pack

[scar3crow]

the skybox looks amazing on some of the pictures.

Thats not a skybox, but rather a sky texture, the same sort of thing that you see normally in Quake. The maps with the cool grey clouds and starry sky is e1m1rmx by czg and Vondur, a tasteful use of a new sky texture. The last screenshot is what we all know as Quake's traditional sky, which I still think looks awesome.

And I've been a map editor for many games, UT2004, CS:S, and Half-Life: 2.

Well CS:S and HL2 use a version of WorldCraft by Ben Morris, which is a Quake editor, that Monster linked you to earlier. They simply renamed it to Hammer and made it a bit more sticky at supporting other games from what I hear. Where would Valve be without the Quake community?

You can find GTKRadiant, which Spirit mentioned, here. This editor is a good bit different than most, but from what I understand it is a bit more respected, and it seems the best mappers use it. It is similar to the editors for Quake3 and Doom3 (the wiki article has a short history of it). I have noticed most game studios want experience with Radiant or UnrealEd out of their designers, more so than other packages.

As for a client, I recommend DarkPlaces as well.

Monster - IIRC LordHavoc uses the latest GTKRadiant now, but Urre still uses BSP and is pretty good with it.