The stealth assassin of TFC, the Spy has fairly light armor and average speed, but has the unique ability to disguise himself as a member of an opposing team. His "special skill" button brings up the disguise menu, letting the player choose what team and what class he would like to appear to be. Enemy sentry guns will not fire on a Spy disguised as a member of that team, making them very capable of penetrating a base's defense. A disguised Spy can also position himself behind an unwary enemy to deliver an instant-kill stab (in the back of the head) with his knife. Attacking with the knife or firing any weapon causes the Spy to lose his disguise, but tossing grenades does not, making Spies the ultimate sentry gun killers. The Spy can also feign death, letting him bide his time as a corpse while he changes disguise or plans his next move. Geared more for offensive support, the Spy is one of the most challenging classes to play effectively, but a skilled Spy can be very disruptive against the enemy team. Even suspicion of a Spy in the enemy team's midst can create a gaping hole in an organized defense, as defenders waste ammunition shooting each other for "Spy checks" (enemy Spies still visibly bleed if damaged) or are lured out of position. It should be noted that in friendly fire-enabled servers that this technique is generally thrown out of the window due to all players bleeding from being shot. However, many servers have friendly fire disabled. The Spy class lacks the speed, armor, and weaponry to hold in a straight-up shootout against most other classes, and any contact with an opposing team's Scout or Spy will cause him to lose his disguise. Because a Spy disguised as a member of the enemy team also randomly adopts the name of an enemy team member, it is possible for a player to see a Spy with their own name, thereby blowing the Spy's cover.
Another potent weapon available only to this class is the gas grenade (sometimes referred to as a "pill" due to its shape and colors), which has a temporary hallucinatory effect, causing enemies to see and hear phantom explosions, shots, flames and tossed grenades for a short period of time. This relatively harmless effect masks the fairly moderate damage over time the grenade causes while an enemy is in its area of effect. In large doses, the Spy' gas grenades can cause severe damage.
Rounding out the Spy's unique arsenal is the tranquilizer pistol, which fires a special dart that does negligible damage, but greatly reduces its target's rate of movement temporarily. It is best used on faster classes to facilitate a lethal knife strike. The Spy is also armed with the double-barreled shotgun, nail gun, and up to 4 normal grenades.