Monolith[1] made some of my favorite games growing up.
It started with Shogo, but also No One Lives Forever, Tron 2.0 and F.E.A.R. left deep impressions.
What stood out was the combination of their well-done 3D engine with world building and art direction.
It wasn't the same from game to game, each game had their very distinct feel, and always interesting.
And I think few shooters have as good enemy AI as the goal-oriented[1] ones in F.E.A.R. (sadly not used in the sequels)
Good times, good times...
[1]: https://en.wikipedia.org/wiki/Monolith_Productions
[2]: https://www.gamedeveloper.com/design/building-the-ai-of-f-e-...