Quake 2 Chaos Deathmatch
Quake 2 is an older game produced by id software. There was a modification for it called Chaos Death Match. This Mod increased the replay value of Quake 2 by adding unique weapons, melee functions, grapple hook, power ups, and much more. The added elements gave Chaos DM a highly dynamic multiplayer experience that doesn't stagnate like most vanilla First Person Shooters.
Since it is so old, not many people still play it. If you are interested in playing, you will need to have the Quake 2 game files, Chaos mod files, a multiplayer server browser app such as qtracker, and you should sign up for the Chaos Facebook Group The Facebook groups is ran by Trixie Moo, who organizes weekly games on the Moo Server. It is a closed group so you need to get an invite.
Here is a playlist of past games