The Buff Banner and bugle is one of the Soldier's unlockable weapons in Team Fortress 2. Its appearance is a backpack with a flag with a picture of an explosion attached, which also comes with a bugle. There is a rage meter that can be filled by dealing damage, once it's filled use your special attack button (default is right-click) to blow the bugle. It forces you to taunt with it, making you completely vulnerable while it lasts, and though you can move, you cannot switch weapons or attack in any way. After that all damage dealt by the Soldier and nearby teammates will be mini-crits. This only lasts for 10 seconds, so use it wisely. If you buff an Engineer and he builds a Sentry Gun/is near it then that Sentry will also deal mini-crits. There are two separate calls for both teams. During the buff, all team members within the range have a team-colored ring at their feet not unlike the Quick-Fix's ubercharge, and they will deal mini-crits. A Soldier has to do about 600 damage before this can be activated. This is great for a Sniper with the Bushwacka equipped, for all their melee attacks will be critical hits due to mini-crits always being critical hits. A Bushwacka critical hit deals a heavy 195 damage. Projectiles already shot such as Huntsman arrows, rockets, grenades will all still mini-crit as long as the owner of it is in the Buff Banner's range when it hits the target. 
Item icon Festive Buff Banner

A festive buff banner.

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