Ultiduo

Ultiduo is a competitive format consisting of two players on each team, a Soldier and a Medic.
This gamemode is played on small KOTH maps that are specifically made for it. Ultiduo is often played by the 6v6 combo, containing the Medic and Pocket Soldier, to build up synergy between each other.

Weapons

ETF2L has a whitelist for Ultiduo allowing the default loadout for both Medic and Soldier with few unlocks for both.
Naturally reskins of stock weapons (e.g. strange weapons, festive weapons, botkiller weapons, the Frying Pan, Conscientious Objector, ...) are allowed.

Soldier
The Disciplinary Action
The Original

Medic
The Blutsauger
The Ubersaw

Maps

ultiduo_baloo
koth_ultiduo_r_b7

Competitions

Ultiduo cups are often held by leagues or sponsored by community members. As each team requires only 2 players these cups are usually easy to set-up, making it a viable option for offseason cups.

It is generally very welcomed by top players as it is a very good source of practice and it is also widely considered to be a fun gamemode.