Psychophobia is a Doom II mod which can be played with gzdoom and skulltag. Features: new weapons, new monsters, new textures, new music, new sounds, new decorates, new Hud, new maps, and many other different things.
This review may contain spoilers
Magnificent level design - perhaps better than Hellcore, some levels are reminiscent of games like Diablo 2, Blood and even obscure classics like Powerslave. Great detail and immersion.
Spectacular atmosphere - brings the best out of the two basic settings of Doom: Dark, gritty futuristic action and chilling, obscure medieval combat, with an incredible variety of new textures that can be set to hi-res.
Quite challenging - increased difficulty every map, medieval maps specially.
Great enemy placement, variety of foes
Wide array of options - from a old pc to a high spec one, this mod can be played with different graphic options with shortcuts to each setting
An arsenal of deadly, reloadable weapons - from classics like the BFG9k to additions like the flamethrower and different types of grenades and magic spells.
Bottom line: Definitely one of the best Doom II mods out there if not the best of all. Extremely underrated.