BZFlag

BZFlag (Battle Zone capture the Flag) is a free, open-source 3D multiplayer tank battle game. Originally developed in 1992 for SGI workstations, it is now maintained for Windows, macOS, and Linux.

Gameplay Features:

* Game Modes: Primarily features Capture the Flag (teams battle to bring an enemy flag to their base) and Free-for-All (players aim for the highest individual score).

* Power-up Flags: Players can collect "super flags" that grant special abilities, such as jumping, cloaking, or laser fire. Some "bad flags" can impose disadvantages unless removed with an antidote.

* Teams: Players are divided into Red, Green, Blue, Purple, and Rogue (independent black tanks) teams.

* Customization: The game uses a BZW map format, allowing users to create and host servers with unique layouts, physics (gravity/speed), and sky colors.