I know ♣ Jacket ♣ already did this BUT I will still do it:

Scout:
Recruit's Metalplate
- A secondary which should make the scout a bit tankier with +25 max. Health and 30% Flame-Resistance with the cost of, well a secondary, 10% speed and a ''Heat-Meter'' which is filling up when burned by a pyro. When filled up, you will gain a speed boost but will lose you max. Health and you have to pick up your Metalplate or you have to refill it at a locker.

Soldier:
- Pyroman-Build Boomstick - Well, if the Pyro build his Flamethrower one time he can do it again. This weapon is the lovechild of the Rocket Launcher and the Flamethrower. You can switch between 3 modes (I know the Vac is enough but hey!); You can charge a shot which will throw you back because the soldier did not do a good job on this, you can change it to a bit larger explosion, a flame explosion or a rocket that when it hits someone, will automaticlly fire a shotgun shot on the other side of your target.
- Light-Footed Tankbuster - Another secondary for the soldier which makes him run 25% faster with nothing else

Pyro:
- Experimental Liquidthrower - Well, Valve said the Pyro was Pyromaniac which his name gives away BUT screw it. This weapon has a -20% Dmg penalty. Also a 3 mode weapon which gives you the ability to store mad milk and jarate (don't know if it should be stored ''charges'' which you can throw yourself then). Underwater it just functions as an automatic Airblast as well as water is the only possibility to refill this weapon (besides lockers)

- Maskedmans Airtank - Repurpusing the gascontainer of the flamethrower to an oxygen-container this will give you double underwater time at the cost of -10% primary ammo

Demo:
- One-Man Artillery - Pipes will explode on any impact but will deal -10% DMG, have a 30% increased projectile speed and a 20% decreased fire rate.

Heavy:
- Sowjets Anti-Coward Gun - A minigun which has a 10% DMG penalty, 50% increased ammo and a DMG bonus of 50% agains enemys in the air.

Engineer:

- The Sodium Experience - A Pistol which has a fire rate penalty of 10% and a clip/ammo penalty of 25% but it fires bullets which will deal a realy small explosion if they hit a player. In case I would say it is like a rocket/grenade explosion with a -90% explosion radius or something. And yes the DMG should be the bit of the bullet + the explosion DMG which is... let's say a solid 15. Also useable by the scout. And I totally did not got this idea because I watched a vid in which Sodium-filled bullets were been show. ^^

Medic:

I have seriously no ideas for him

Sniper:

...

Spy:

:I