Because GoG finally add classic Doom 3 I can start playing some fun mods.
I would like to share with You Phobos mod by Team Future.
https://www.moddb.com/mods/phobos
By size it is not simple gameplay/graphics modification or another single map, it is in size of RoE mission pack.
There is new protagonist with own goals and problems.
There is new story with expands D3 universe with new characters, factions and new demons.
Guns have been rebalanced, there is new shotgun model.
Imps are now much more aggressive and gunfights are more challenging.
Levels are well made, with many details, many dead ends, interesting puzzles.
Right now there is available prolog, episode one and episode two, episode three is still in development.
and it is for free :)