Epsilon (Quake)

Quake Epsilon is a graphically enhanced build of shareware Quake 1 for Windows/Linux/Mac, which can be upgraded to the full version of Quake along with it’s mission packs Scourge of Armagon and Dissolution of Eternity by copying the full-version .pak files into the correct folders.

It’s made out of the Darkplaces engine and many mods from members of the Quake One forums and elsewhere

This one probably won’t tickle the fancy of the purists.

However, I recently did an SP play through of Quake and all the official mission packs, using Epsilon on Ultra settings with HD textures. It was so much fun. It was classic Quake campaign gameplay, but with a new shine.