reQuiem is a custom OpenGL Quake engine for Windows and Linux. It's designed for maximum compatibility with all things Quake - past, present and future. It's fast, reliable, and easy to configure. In short: it fixes what was broken, improves what needed improving, and leaves the rest alone.

Download reQuiem for Windows and Linux. And check out the project at GitHub. Here is a better working but very beta and not meant for archival zip:

The readme says

  • expanded limits (edicts, models, lightmaps)
  • mp3 and ogg music
  • playback of demos from FitzQuake 0.85, aguirRe's engines, and QW
  • demo pause, rewind, fast-forward and quick-seek
  • dzip and zip/pk3; also compression of recorded demos
  • Nehahra, -quoth, and multiple -game arguments
  • md2 and md3
  • console tab-completion for cvars, commands, and filenames (maps, demos, sky, etc)
  • Options menu containing most useful settings, intuitively grouped
  • support for non-US keyboard layouts

But it also features

  • Automatic detection of limit-breaking maps. Switching to protocol 10002 when needed.
  • Fast and convenient video capture support. Just type "capturedemo demoname" and it will output an uncompressed AVI file of the same name. You can specify things like the framerate or resolution.
  • Pasting your clipboard into the console
  • Detects the fish count bug and fixes it internally.
  • MH's beautiful sky rendering
  • Compatibility options like "ignore the case of filenames",
  • built-in reverse weapon cycling: if a custom progs.dat doesn't have impulse 12/CycleWeaponReverse functionality, reQuiem can provide it.
  • client-side support for the new Fitz protocol (including demo playback)
  • screenshots taken while a map is open now get named after the map
  • all data from Quake Pre-Release/0.8/beta3 works

Runs on Linux and Windows. On Linux it uses OSS, with FMOD for the music.