Quake II RTX
The classic (and now quite old) shooter was recently given a facelift by a developer working with nVidia. Check out the way ray-tracing is introduced into the environment of this major late-'90s game.
(Disclaimer: Quake II is rated 'M', so expect late-90s levels of blood and gore)
I logged so...very...many hours playing this over the years. :)