Team Fortress 2/Spy

The Spy is perhaps the strangest class in TF2. Though he is not effective in direct combat, he can use a combination of cloak and disguise in order to infiltrate the enemy. His knife produces an instant kill from behind and his sapper can disable and destroy buildings, making a good spy a huge asset to the team.
 * Health: 125
 * Speed: 100% (93% disguised as demoman, 80% disguised as soldier, 77% disguised as heavy)
 * Type: Support
 * Special Ability: Cloak

Primary Weapons

 * Revolver - Clip Size: 6 - Reserve Ammo: 24

The revolver is not really meant for heavy combat; while the rounds are more powerful than a conventional pistol, they fire slowly and come in clips of six. Use this weapon when getting away from enemies, running from Pyros, and helping your teammates kill an enemy from a distance.

Secondary Weapons

 * Sapper - Infinite ammo

Clicking on an enemy building in melee range will plunk one of these down on it. Once it's on, a structure will be unable to perform it's function and will slowly lose HP until it is repaired or dead. An engineer can remove a sapper with 2 hits of his wrench, but you can resap immediately if you wish.

Melee Weapons

 * Butterfly Knife

This weapon instantly kills if you stab from behind (and sometimes the sides). Attacking from the front, however, deals less damage than a normal melee weapon would. The most obvious situation to use the knife is for assassinating enemies, but if you're locked in close-range combat, you can whip out the knife and try to flank the enemy for an instant kill.

Using the Spy
The spy is a stealth class, first and foremost. While you can put up a fight with the revolver, your role is better filled by getting behind enemies and stabbing them in the back.