The spoiler is a spy! This is actually Spy-related stuff.
Disguise as a heavy.
Why, I hear you ask?
1) No spy will disguise as a heavy normally, because of the speed nerf that applies when you're not in cloak, and most people are aware of this. Thus, less suspicion.
2) Because your primary requires spinning up and slowing yourself right down, people won't expect you to be shooting randomly (compared to, say, pyro).
3) The aforementioned speed nerf does NOT apply when cloaked, thus for most of your trip, you'll be fine.
4) Medics like you.
Good luck backstabbing anything ever then >_>
Not necessarily true, while you indeed will have issues backstabbing a moving force, one which is rooted in place will be much more prone to your attack, typically if you are going to use the heavy disguise, do so when the enemy is on the defense, or in a staging area.
More like "good luck getting to the enemy base ever", what with random spychecks.
You wouldn't believe how often I get spychecked as <insert class here>.
Here are the more terrible disguises:
Scout: Noticeably slower than regular scout. If you ARE going to disguise as scout, at least have the decency to jump around and shout,"Need a dispenser here!" constantly, like the actual thing.
Engineer: Not wrenching, not carrying toolboxes
Medic: You can't heal anyone.
Spy: I really shouldn't have to explain this one.
Disguise tips:
When you disguise as a sniper on their battlements, make sure you're at least pretending to snipe. Crouch to move slowly like a scoped sniper.
Flip through your disguises until you find someone who is damaged. Then, cloak(unless you have the dead ringer) and walk backwards towards the enemy base. You wouldn't believe how many people I've tricked with this one on 2fort.
Suit your weapons to what's happening during the battle.
Need to kill people faster? Take the ambassador or the enforcer depending on how often you get headshots.
Get spychecked too much? Take a spycicle with you for good measure.
Running out of cloak too fast to get to the enemy base? Take l'etranger or the Big Earner.
Problems with spychecking engineers? Take out Your Eternal Reward.
Find yourself destroying a lot of buildings? Bring on the Diamondback, and use those crits to destroy the enemy team.
I personally find myself using Spycicle/Ambassador/Dead Ringer a lot. Mainly because I find it more fun. Though, were I a sadist, I'd take the diamondback. I tend to sap a lot of engineer nests
.
Unfortunately, pyros seem to be catching onto the powers of the spycicle. I really wish Valve had made it so that being set on fire while you have the spycicle out ensures that you don't scream about fire.