Zerstörer - Testament of the Destroyer

For its age it is certainly very impressive. New enemies, weapons, and effects that had yet to be scene in Quake for its era. Played in 2022 however, it is hard to look past the often flat combat and clunky level design. Still, you could find worse uses for your time.
The only reason I am rating this just "Good" is its age. I remember when I first played this way back in 1997. It blew me away back then, a proper milestone in Quake modding that everyone should give a go.

IIRC it also is the first mod with cutscenes, or at least one of the first. Some of the levels are a bit jank, but the overall atmosphere is great, and it has fun weapons and some decent new enemies.
Few releases have such a compellingly forboding and unfriendly atmosphere. Made in a long bygone era, this is not the most visually appealing, but nonetheless a classic treat and one that will forever haunt the memories of those who delight to romp through it.