The Medigun is the default secondary weapon for the Medic. It is a modified fire hose nozzle wrapped in tape and outfitted with a bottom handle and is connected to the Medic's backpack by a hose. It fires a glowing team-colored beam into the recipient, who will then appear to exude similar colored cross symbols, similar to a Teleporter trail. When a disguised Spy is Overhealed, enemies can also see the team-colored crosses, giving away the position of the Spy. This weapon heals players at a rate of 24 a second, an if enemies haven't been damaged for 10 seconds, the healing rate is tripled to 72 health per second to encourage falling back to be healed as players often found that fighting to the death, dying, and respawing was faster than being healed back to full health with the 24 health a second mode. The Ubercharge of this weapon makes the user and the Medic healing invincible to all player attacks, sawblades on Sawmill, trains on Well, drowning, Backstabs but not Telefraging. This lasts for 8 seconds and users being Ubercharged retain their current model but are colored by a solid shiny team-color surface with yellow eyes on RED team and purple eyes on BLU. This animation is the same for all Ubercharges.
In the "Meet the Medic" trailer, it is implied that the Medigun can only heal wounds that a body normally could recover from, since the Medic states "Ribs grow back", then tells his bird Archimedes that they don't, which implies the Medigun also cannot heal them.