TF2 Spy Disguise Kit
The first thing a Spy has to do is disguise. Commonly, you will disguise as an enemy unit, but as which one? Of the nine, there are five that move at the same speed as the Spy: Demoman, Engineer, Pyro, Sniper and the enemy Spy.
The best to disguise as is either the Demoman, Engineer or Sniper. Being an enemy Spy is ineffective because there is rarely a Spy walking around without a disguise, so this will instantly alert the enemy. Of the three left, the best is the Engineer. This is because 95% of the time, the enemy team has an Engineer.
Don’t disguise as Pyro, because Pyros are known to be trigger happy Spy-checkers. When they notice you aren’t Spy-checking, this is going to cause some confusion.
Never try to disguise as a Medic or Scout. You will move slightly slower than the Medic, but what is really going to alert the enemy is that you aren’t healing everyone. If you’re the Scout, it’s going to be a dead giveaway that you are moving incredibly slow.
The Soldier and Heavy, which both move slower than the Spy, can be effective for gaining access into the enemy’s side because they are rarely checked, but they are terrible when trying to attack an enemy, because every other class moves faster and you won’t be able to catch up.
The best overall disguise is the Engineer, followed by the Demoman and Sniper.