Which primary weapons do you use for each class and why?

because I need advice from good TF2 players.

Scout: Scattergun, overall probably the best Scout gun due to it not having any downsides.
Soldier: Rocket Launcher, same with Scattergun. Can't deal with less damage or a smaller clip size.
Pyro: Degreaser, combined with Flare Gun and Axtinguisher you can easily chop of people's heads and make them feel ashamed of trying to fight you head-on.
Demoman: Grenade Launcher, can't deal with a smaller clip size or having a bit of extra health in exchange for losing a weapon.
Heavy: Mini-gun, no downsides
Engineer: Shotgun, again, no downsides to it and does respectable damage. Frontier Justice if I've playing Battle Engi because of mini crits.
Medic: Crusaders Crossbow, very useful ability of healing teammates from far away.
Sniper: Sniper Rifle, again, no downsides.
Spy: Revolver. And yet again, no downsides.

I mainly use Stock items because they have no downsides and do respectable damage.

Well once again stock weapons are the best on my opinion

Stock is best. I will agree with that. Even though I <3 my pencil pusher (S. Pro KS Machina), I do prefer normal sets most, since they have no negatives.

Stock weps for everyone basically.
-although the sydney sleeper holds a special place in my heart with how its a good support gun. it also helps that im not good at headshots.
-the crossbow for the medic is strangely helpful in multiple ways. I tend to get random kills or a heal bolt for about 100 health that turns the tide

I love the dead ringer + spycicle for spying. The spycicle protects you from pyro checking for a few moments, and the dead ringer totally fools your enemies, letting you sneak behind them and turn them into epic ice statues.

Scout = Scattergun
Solly = Original
Pyro = Degresser + Axtinguisher
Demo = Grenade launcher
Engi = Frontier Justice for Battle Engi / Rescue Ranger for MvM
Heavy = Minigun / Iron Kurtain
Medic = Crusaders Crossbow
Sniper = Stock/AWPer
Spy = Ambassador

Scout: Stock Scattergun because it has no downsides. Quite effective too compared to other Scout Primaries.
Soldier: Stock Rocket Launcher because again, it has no downsides. Also, Direct Hit is a bit too hard for me to use as you can't spam choke points, etc. I also hate the low clip on other Rocket Launchers.
Pyro: Degreaser because I can quick-switch to Reserve Shooter after an air-blast or Axtinguisher if I am up close.
Demoman: Stock Grenade Launcher because I can't rely on small clip size and I just can't replace a weapon for health-bonus fancy shoes unless it is Degroot Keep of course.
Heavy: Stock Minigun as it has no downsides. Hate the slow speed of Brass Beast. Heavy is slow enough! xD
Engineer: Stock Shotgun because I don't like low clip size unless it is Frontier Justice + Gunslinger.
Medic: Blutsauger because if you dodge well enough and the person you are healing is good enough, the downside of a bad health regen isn't so bad after all. Also, it is good for escaping from challenging situations, especially against Pyros.
Sniper: Stock Sniper Rifle as it has no downsides. Huntsman if on Degroot Keep of course.
Spy: Big Earner as I use this with Dead Ringer. When I feign a death, I need to get the invisibility charge bar thing (whatever you call it) up as quick as possible in case I get into a sticky situation again and I cannot cloak.

There you go, the Primary weapons I use. Please don't start a war because of possible bad choices. Thanks.

Scout: Stock because I have nothing else to use.
Soldier: Stock/Original for combat. Direct Hit for building demolition. All the other rocket launchers are either too difficult to use or too bad imo.
Demo: Stock, most op weapon.
Pyro: I don't play pyro so idk.
Heavy: Stock, all the others are too situational.
Engi: Widowmaker for attack because I can aim with a shotgun (it teaches you to do so), currently trying the Frontier Justice.
Rescue Ranger for defense if I can trust my teammates to protect me, otherwise, stock.
When I'm feeling particularly douchy, I go pomson.
Med: I almost never play med, so probably stock.
Sniper: Stock is the best.
Spy: I don't even touch spy.
So yeah. I play engi (my main), sniper, and sometimes heavy. I suck with every other class.

Scout: Soda Popper, because 5 jumps can help you get places, I guess
Soldier: Liberty Launcher, because I'm retarded and need the rocket blast damage reduction, so I can rocket jump
Pyro: Rainblower, because Pyroland
Demoman: Since I play Demoknight, I suppose I have to say my sword, which is a Persian Persuader. Though, my secondary loadout, I use the stock Grenade Launcher with Sticky Ullapool
Heavy: Natascha because I really do enjoy slowing people, and you have 50% extra ammo, so that's nice
Engineer: Frontier Justice, because it goes great with the Gunslinger
Medic: Crusader's Crossbow, because it's a rather nice weapon, healing people far away and all
Sniper: Hitman's Heatmaker, just because I really like it
Spy: Ambassador, because I have nothing better to use

Scout = Stock Scattergun, is the basic and best
Soldier = Original, launcher in middle of screen
Pyro = Stock Flamethrower (strange), basic and best
Demoman = Stock Grenade Launcher, basic and best
Heavy = Iron Curtain, reskins are cool
Engineer = Stock Shotgun, basic and best
Medic = Stock Syringe Gun, basic and best
Sniper = Hitman's Heatmaker (strange), teaches me to aim for the head
Spy = Stock Revolver, basic and best

Scout: Stock, reliable damage
Soldier: Black Box, stay alive longer
Pyro: Degreaser, the deadly combos
Demoman: Stock, hate the others
Heavy: Brass beast, damage is nice and movement speed is unnecessary anyway
Engineer: Frontier Justice, the crits are nice to help you escape after your sentry's down, and protect its successor
Medic: Crusader's Crossbow, powerful and has the long-range healing
Sniper: Hitman's Heatmaker, focus is helpful and I don't want to bodyshot anyway
Spy: Diamondback, crits are nice