Duke Nukem 3D, The first game to use the Build engine, was when it was released outstanding, with slooping floors and rooms over rooms and with a bad attitude.
And since it had the best level Editor I've seen, Many people made maps for Duke, and I was no exception. These maps, unlike Dooms are mostly completed.
Although it is old and by modern standard bad, I still kinda like it, it's fast meaningless action with an attitude!
I whish that there will be a OpenGL Patch or something patch, 'cause it deserves to live longer, as with both doom and blood..
I'll put up my maps here someday