Spy

The spy is a suave backstabbing rogue that has the ability to one-shot any class in the game with their knife. Spies are valued in that they can get important picks through the manipulation and deception of the enemy team. The spy arguably has the worst direct combat ability, as it is solely designed to only get one or two kills at a time. As a pick class, the spy will usually target the enemy Demoman, Heavy or Medic and either get the Medic to pop his uber or to drop his uber. Spy is capable of incapacitating and destroying the Engineer's buildings.

In Sixes

Main Article: Spy (6v6)

In the sixes format, the Spy is considered an offclass. It is most often run when one team has a disadvantage and they need to try and create an advantage (usually through dropping the enemy Medic's uber).

In Highlander

Main Article: Spy (Highlander)

In highlander, the spy has the same role: it is often used to pick the enemy Medic, Heavy, Demoman, or other picks most valuable at certain moments (most often the Engineer). As there is a full-time Spy in highlander, it is often considered harder as the enemy team has a full-time Pyro and is spychecking more often, leaving the Spy with less opportunities for picks.

The spy also provides important information to better help your team. As a spy you can read what medi gun the other team is running and also find out what percentage they may have. You can also be a perfect surveillance tool, you can easily see where the combo and other classes are going, giving your team the advantage of knowing where they are moving along with knowing where to push toward.