Regardless of game mode, Spy's job remains the same. His primary goals are to:
- Assassinate high priority targets that other pick classes (Sniper, Scout, and Soldier) cannot reach.
- Relay enemy positions, pushes and Ubercharge to his team. The location of the Sniper and the Medic's Ubercharge meter are especially important.
- Sap the enemy Engineer's buildings to allow his team to push forward.
Due to Spy's low health, average speed, and poor damage output, he will usually be shut down when he attempts to gain picks. Enemies are typically on the lookout for him, and when he becomes visible, he will often be called out and killed. Thus, he often must attempt suicide plays, trading his own life for that of a more-important target - escaping with his life is secondary. Oftentimes, Spy will finish a match with more deaths than kills, but if he lands kills at the right time, his team can push forward, gain momentum, and win the game.
While not terribly effective for deceiving the enemy team, Spy's disguises are a valuable source of information; he can examine enemy players' loadouts - especially the enemy's Medi-Gun - by disguising as them, allowing his teammates to adjust their positioning and loadouts accordingly.
Unlike Sniper, Spy's ability to gain picks is very limited. The better the enemy team communicates, the weaker he becomes. At high levels of play, his effectiveness at assassination diminishes, which makes him expendable. This allows him to fulfill a variety of unconventional roles. Aside from his primary goals, he can distract the enemy team by revealing himself, intimidate them with friendly disguises, or lure important classes out of position. Spy may also initiate captures by decloaking on the objective, and may be able to win games on 5CP maps with this technique of "back-capping."
Even if he cannot secure a kill, Spy's ability to instantly kill any class from behind makes him a valuable distraction. Revealing himself at a distance can distract the enemy Sniper, who may shoot him while his team's combo crosses the sightline. Decloaking behind the enemy combo will often cause them to whirl around in a panic, creating an opening for Spy's team to push in. Even the constant looming threat of a Spy backstabbing them as soon as they lose focus can cause paranoia in players, causing them to make mistakes that Spy's team can capitalize on.
On maps with tighter choke points or against vigilant teams, Spy may have difficulty slipping behind enemy lines. In this case, he will often equip the Dead Ringer and join the flank, chipping away at the enemy's health with his Revolver. While this playstyle does give up the ability to land key picks, it may be better to deal moderate damage consistently than to die repeatedly in an attempt to kill a high-priority target.
At the current state of Highlander there are mainly two different Spy playstyles which dominate the meta. Both styles are used between all divisions, and neither is clearly superior to the other - though one may be more effective in certain situations. The two different methods of playing Spy are called Gun-Spy and Knife-Spy. Note that Spy's Revolver and Knife are by no means exclusive to the Gun-Spy and Knife-Spy playstyles; the terms simply describe which weapon Spy emphasizes in his loadout.
The Gun-Spy playstyle typically utilizes the Revolver or the Ambassador, depending on the situation. The Dead Ringer is sometimes equipped to improve Spy's survivability. While the Revolver deals more damage-per-second, the Ambassador deals greater burst-damage, allowing Spy to kill weakened targets before they can retreat. When using the Gun-Spy playstyle, Spy puts himself at significantly less risk than he would when focusing on his Knife, allowing him to remain alive longer, and provide more information to his team. Simply staying alive to relay enemy positions, tactics, and Ubercharge can be of great value, especially on maps where sudden tactical changes can make a huge difference on the outcome of a match, such as Steel. Remember that Spy can still use his Knife as a last resort to attempt a Trickstab on an overconfident attacker.
The classic Spy playstyle is known as the Knife-Spy playstyle. Spy will go for picks with his knife, eliminating key targets instantly. In general, the only two knives Spy will use are the stock Knife and the Spy-cicle, as other knives make it more difficult to land a backstab by reducing Spy's health or cloak time. All of his watches are useful depending on the situation: The Invis Watch allows Spy to roam large distances on maps with plentiful ammo pickups, the Cloak and Dagger allows Spy to gather information at little risk to himself, and choose the exact moment he decloaks, and the Dead Ringer gives Spy a nearly-guaranteed escape. If caught before he can land a kill, Spy will often switch to his revolver to cause as much damage as possible before dying.
Sometimes, Spy must switch playstyles to maximize his effectiveness as the game-state changes. Consider learning both playstyles to use depending on the situation; neither is superior in every situation.