Total conversion
From DoomWiki.org
A total conversion (TC) is a PWAD that replaces all or almost all of the resources used within the original game. The first total conversion was the Aliens TC developed by Justin Fisher. Other well-known examples of total conversions include Batman Doom, HacX and Action DOOM.
A virtually complete collection of total conversions can be found at Doom Wad Station including not only the above mentioned tc's but also such notables as Hellraiser tc, Duke Nukem tc, Blakestone, Alien vs. predator vs terminator and many more. There is also a section on the site dedicated to Doom3 total conversions - Doom3 total conversions. Amongst the notables are the critically acclaimed Last Man Standing, In Hell and Frankenstein to mention a few.
Freedoom is not a total conversion, but the project intends to replace every resource in the Doom and Doom II IWADs.
