Smash Bros. is a SourceMod plugin and server modification for Team Fortress 2.
As implied by its name, this mod is based on the gameplay of the Super Smash Bros. series. As opposed to damaging enemies until their health reaches zero and they die, damaging enemies instead raises their damage percentage. Enemies with higher percentages take more knockback when hit, with the goal being to knock them off the stage.
The Smash Bros. mod uses a variant of Arena mode, giving each player 3 lives. Players start at 0%, displayed in the bottom-left of the screen. Hitting an enemy will raise their percentage based on how much damage would normally be dealt; the percentage of the last enemy to be hit is visible on the bottom-right for a few seconds. (Similarily, Medics that heal players will decrease their percentage.) All weapons deal knockback; the goal is to hit enemies so they are propelled out of the map and are killed by the deapthpits placed outside the playable boundaries (or simply by hitting the walls or ceiling of the skybox). Due to this knock-out mechanic, the mode requires unique maps which are surrounded by kill triggers both horizontally and vertically, denoted by the prefix sb_.
In addition to the knock-out gameplay, all players have infinite ammo for all weapons (aside from some exceptions, such as the Heavy's miniguns). However, some weapons are restricted, like the Scout's primary, or automatically set to a certain weapon, ex the Engineer is set to have a Wrangler and Gunslinger. Most maps do not have any health or ammo pickups available, instead dropping pumpkin-shaped pickups at random locations that provide random effects when picked up.
Due to the mode's emphasis on knockback, the ability to airstrafe and hit airshots is important to not only survive longer but knock out opponents that are not yet damaged enough to simply blast away.