Open Fortress

Open Fortress is free and easily configured mod for Valve's Team Fortress 2 created by over a hundred developers from the Team Fortress 2 community. It includes a new character, the Deathmatch mercenary, new and modified weapons, and over 50 maps. It also introduces the deathmatch game mode from Quake. Other additions include all the playable characters from Team Fortress Classic and the game mechanic of bunny hopping.
On September 10th, 2021, Open Fortress, along with the mod Team Fortress 2 Classic were removed for download due to an arrangement with Valve. By July 1st, 2022, both mods were once again available for download. 
Gameplay.
Game modes in Open Fortress include deathmatch, Capture the Flag, and duel. In the deathmatch game mode, players move quickly around the map, trying to kill as many opponents as possible. Weapons and powerups are available around the map. The gameplay of deathmatch is based on Quake. In Capture the Flag, players attempt to bring the objective from the enemy base to their own while preventing the enemy from the doing the same. Variants of the game mode are played with the deathmatch mercenary, the mercenaries of Team Fortress 2, or both. Duel is a game mode where two players fight in an arena until a certain number of kills is achieved. This is similar to the unofficial game mode of MGE in the TF2. Other game modes include arena, where players do not respawn and each team attempts to wipe out the entire enemy team, and arsenal, where players face off against waves of computer-controlled enemies.