First Slot: Revolver
Weapon Type: Pistol
Damage: Moderate
Effective use time: 25%-30% depending on the user.
The revolver is a 6 shot pistol. It has moderately high damage and can be effectively used when running, or helping a front line push with there is no way to get past the heavies spamming Natascha next to a dispenser. It should not however be used to kill inside their base unless you are retreating. The only good time to use it when on a "mission" is to destroy an object faster (mainly sentries, although other buildables can be just as important at times).
Second Slot: Electro-Sapper
Weapon Type: Tool
Damage: None (High to mechanical structures)
Effective use time: 45%-70%
The Electro-Sapper is a neat little tool. It allows the spy to temporarily put a Sentry gun (Herein referred to as an SG) out of commission. It will eventually destroy the gun, after about 5 seconds (?). Here is the prime use for the S&S. The S&S can be as simple as Mouse1, Q , Mouse 1 or vice versa. However it can also be very hard to time. I will cover it more in the tactics section.
Third Slot: Butterfly Knife
Weapon Type: Melee Weapon (Knife)
Damage: Low < X < Moderate (Instant Critical Hit, a one hit blow, from Behind)
Effective use time: 75%-100%
Ahhh the knife. The weapon everyone has a love/hate relationship with. When switched to, the spy does a little flick motion, which is commonly spammed by spys, either by habit, wanting to look cool (even though no one else can see it), or keeping reflexes high. This weapon is the bread & butter and the freakin' drink, vitamins, plate, bowl, spoon, everything! of the spy's arsenal. There are a couple of good stabs, which will be covered in a later section.
Forth Slot: Disguise Kit
Weapon Type: Tool
Damage: None
Effective use time: 100%
I don't know a spy who will NEVER use this thing if given a good chance to. Basically, you look like the class you choose when you pop it open, with a random name from someone on the team you choose. (It is not confirmed that disguising as a member of your team will give you a new name). The - key toggles the team color, from enemy to friendly. The friendly disguise is good for playing off near the front lines, or during the setup phase. ***As of the scout update, you may now choose the weapon you are shown wielding. To do this, press the "Last Disguise" key (default: B) while already disguised. If you are holding your knife, you will hold their third slot, if you hold your Revolver, you will hold their first slot, etc***
Secondary Fire(all Weapons/Tools): Cloak
Weapon Type: Tool
Damage: None
Effective use time: 200%
The Cloak. There's not much to say... right click while holding ANY spy weapon/tool and you will go invisible for a short time. Give it about one second to fully cloak. As of the scout update, ammo boxes and fallen weapons give you more cloak time. So sidestep into fallen enemies/friends and grab the ammo to get a longer cloak. This allows the spy to go much further distances.
3. Tool Use
Each of the three tools at the spy's disposal are very useful and play a major role (at least, they should) in our "missions". The Electro-Sapper for instance is used to stop a SG from firing. Although it can be a removed, it still forces at least 1 second of non-fire, so co-ordinate with your team. S&S'ing is very useful as well, but that will be covered in the Weapon Use section.
Next up, the Disguise Kit. Not much to say in ways of strategy. I prefer to switch up disguises every couple of times. Your main disguises should be Demoman, Engineer, and Pyro. I find uses for scout and soldiers as well though. Basically, change as the battle changes and you should be fine. Note it takes one second for your smoke trail to dissipate.
Finally, the cloak. Again, not much to say. Basically, cloak behind a corner, and run out to the enemy base. If you are uncloaking, hide in a not-so-obvious way, like in a corner! Common sense is your friend.
4. Weapon Use
Ahh finally, a part I can actually write about!!! Good, good... Okay, first up, we have the revolver. This weapon is your "Oh sh-t, run away" weapon as well as "No way through the front line... SHOOT!" weapon. It can finish off an enemy you stab with 2-4 hits. Pretty nice little toy, never used enough. It can also be useful for when your team is attacking and your kinda off to the side, but you can't get to any enemy to stab, so you just pop it out and let cartridges roll.
Knife Time! This little mini-section will teach you, very basically, how to perform some of the stabs most spys will use. I will assume you already can cloak, disguise, and play off your disguise.
St-Stab - Stalk Stab: The St-Stab is very simple and can be used by even the newest of spys. As the name suggests, it is all about getting behind an enemy while cloaked, and uncloak while running behind him/her. Truthfully, this is more useful for defender teams on Capture Point, as they can stalk the stragglers/medics and begin a CS(Chain Stab) epidemic. However one thing you must be mindful of is the extra straggler who can come around even further behind the others, and kill you as you uncloak, ruining your tactic. An easy anagram to remember is CASC: Check, Appear, Stab, Cloak.
^Stab - Stair Stab: This is a bit harder to perform and doesn't always work the way you want. It can be performed at a VERY low height advantage, as low as the bridges on cp_well over an enemy. What you are going to do it CROUCH-jump over an incoming enemy, turn 180 degrees to face his back, and stab. On paper (internet page in this case) it sounds simple. It's not. It takes precise timing and the Scout update only made it worse. Just keep practicing as much as possible.
!Stab - Flick Stab: Some say this stab can NOT be done since the Scout update. Well... it can. I don't know the trick to getting it to work, but if you can find out, good job. Basically, it's running towards a enemy, having him pass you, and quickly doing a 180 degree turn and stabbing, then 180'ing back and continue on while Disguising.
S&S - Sap 'n Stab: possibly the hardest of the stabs, a sap and stab (sometimes reversed) is as the name sounds. Sap a sentry, kill the wrench spamming engineer, or vice versa. Not much can be explained on paper, just keep practicing. It's hard to do at first, but you will get it.
5. Bringing it All Together
This part of my guide will focus on tying all these tricks together. Lets break down the phases of the game:
CAPTURE POINT/PAYLOAD:
Setup/Early Game: This phase is really just were I jump around and think about where I want to go for the map. But be sure to give yourself 10 good seconds in the Setup Phase to fully disguise and change your disguise weapon to something that is more convincing for your plan. Wait for about 10-20 seconds after the round starts to let the Heavies and the Soldiers stop spamming. Then precede to your chosen location. This location should be a point on the map that will provide ample cover to unlock and act like you went there to attack the "enemies" as they came out. Afterwards, let cloak fill up half-way JUST IN CASE. Then proceed to backpedal, playing off your disguise and see if you can S&S some sentries to allow your team to push up. Another good trick is to hit any medic/_____ combos, then cloak and rinse(refill cloak) and repeat.
Mid Game: The next part of these modes is pretty simple. Cloak in shadowy corners, do what you can in ways of taking out those sentries. Killing the combo runners and performing CS's is a good use of time. YOur main goal is take out defensive people and stop the attacks from keeping your team down. I hope to have videos up soon for some specific map gameplay with my own commentary.
End-Game: This is the most important part where you want to take out sentries. Chances are when things start slipping down that drain, people get really defensive. S&S is a good way to go, but don't get too cocky. You're better to your team taking out one person every couple of minutes, than a sentry that, by the time you respawn and reach the front lines, will be rebuilt anyway.
6. Ending
Blah blah blah, I reserve my right not to have anyone copy me. I am only posting this on my own account, Driek, on TF2Fort forums thus far.
Enjoy! =D
Any criticism, please, I am open on all ears.
I WOULD LIKE TO INCLUDE VIDEOS. CAN SOMEONE TEACH ME THE TRICK TO HAVE IT RECORD DECENT VISUALS WITHOUT SLOWING EVER MY COMPUTER (an awesome Insanitech GT1300 
)I ALSO NEED A WAY TO ADD MY OWN COMMENTARY TO AVI FILES. PLEASE HELP ME!