How to drop weapon:
Suicide while holding it.

1. Walk out of spawn room.
2. Drop any throwable secondary weapon on the ground.
3. Throw it.
4. While throwing animation is in progress quickly pick that weapon up from the ground.
You should be Civilian.

1. Equip Panic Attack.
2. Walk out of spawn room.
3. Equip B.A.S.E. Jumper.
4. Fully load Panic Attack.
5. Walk into resupply closet.
You should be Civilian.

1. Equip Panic Attack.
2. Walk out of spawn room.
3. Empty it's ammo to 1.
4. Drop it.
5. Swap it with panic attack that you are holding.
(After this you should be holding panic attack with 1 ammo left and full one should be on the ground)
6. Shoot last bullet.
7. Pick up Panic Attack lying on ground when shooting animation ends.
You should be Civilian.

1. Equip B.A.S.E Jumper, any stickybomb launcher.
2. Walk out of spawn room.
3. Equip any shield.
4. Walk into resupply closet while holding your secondary.
You should be Civilian.

First way to do this:
1. Drop any minigun.
2. Empty yours by holding LMB.
3. Hold LMB when you have no ammo. (keep it spun up)
4. Pick minigun from the ground.
You should be Civilian.
Second way to do this:
-Same as Pyro-

-Same as Pyro-

There is no known way to do this. Sorry :(

1. Walk out of spawn room.
2. Drop Jarate on the ground.
3. Throw it.
4. While throwing animation is in progress quickly pick Jarate up from the ground.
You should be Civilian.

There is no known way to do this. Sorry :(

Because this glitch utilizes player 'holding' weapon with empty or without clip you cannot attack.
If you'll change your weapon or die your pose will reset.
In Sniper's and Scout's case you should wait until jar stops rolling. It'll make picking it up easier.
After some practice you should be able to do this on first try.
I hope that this was helpful.
Have fun as Civilian!