This section is...well...the intro, i will break out of character for a moment/this section, this was an idea from the last one's comment section, well it originated anyway, I am not making this because my laptop keeps crashing! so i can't play mvm, but that is a factor of it, anyway this may have some sections with the pyro, yeah i will list my characters cosmetics here, just so you can imagine them, i always do it in my stories i make, anyway here are the pybro's cosmetics:
Aperture science hardhat (orange)
Deus specs
Cute suit
And engie:
Ten gallon hat...i named it so i don't know it's real name
Cute suit
Strange Support Spurs
Anyway, on with the characters:

Now the weapons for being a pybro are quite simple, in fact only one is nessesary and even that can be swapped out, but we will discuss what other choices there are for the weapons:
The homewrecker:
+100% damage vs buildings
Damage removes Sappers
-25% damage vs players
This is the most nessesary, but swappable weapon, it destroys sappers, thereby saving the engie's buildings, yet only use it for the sappers, it is useless against players as it has a damage penalty, and...c'mon you have a flamethrower, use that or a shotgun/flare gun.

The neon annihilator:
Damage removes Sappers
100% critical hit vs wet players
No random critical hits
-20% damage penalty vs players
This weapon is more useful against players, especially near water as you crit players from it, but less about saving the buildings, as the other one takes 1 hit to destroy a sapper, this one takes 2.

The shotgun:
It is a good 6-shot beauty of nature, with a wooden grip and a steel barrel, this gray cannon can ruin a spy's ♥♥♥♥ crap



The flare gun:
This 16 shot, slow loading 1 per reload, piece of plastic, can set a spy on fire, stoppping him from escaping, it also does extra damage to people who have already been hit by it, making it great at hitting spies repeatedly (i just noticed how much out of character i have been XD)



Detonator:
Not a very good pybro weapon, is for jumping, and requires alot of teqnique and skill when using it properly. It is good for countering snipers and it takes good judgement to be able to hit then=m while they are hiding behind walls / barrels / etc.




Reserve shooter:
Well i think that you should only use it if you can aim and can airblast properly.





Mannmelter:
Quite useful, in a way, if you'r engie has pyro problems, you can take the fire away and get a crit to take away the problem.







Scorch shot:
This weapon is for the people who cannot aim, and want a splash but less damage for it.






Panic attack:
This weapon...eh it is good, but not really for this loadout.

The most important thing here is that the pybro's primarys should only be used to counter immediate threats. By that I mean not to go chasing a spy around the place when he runs away.
Just use your secondary, its not that hard. The pybro's best primary is this beauty -


It is the stock flame thrower! No airblast nerfs (for deflecting rockets/grenades/huntsman arrows/crossbolts/otherprojectiles) and no damage penalties (for dealing with those pesky spahs).
The tactic for using this is farely simple.
1) Set all enemies that are an immediate threat on fire example : Pyro's spahs and heavys.
2) Do not run after them when you have scared them away with your magnificence.
3) Shoot them with your secondary OR let them run.
4) Conserve flamethrower gas so that you can airblast rockets away or just stay close to the dispencer (but not to close or else the sentry and engi will be under threat)
5) Use the detonater or scorch shot to take out snipers from a distance. If they are not equiped then get another pybro to take care of the nest and take the fight to the sniper OR just persuade the other team mebers to take him out for you.

The backburner: (Sentry took this section, i thought diff would do a little more, but i don't blame him, this is quite hard/annoying)
This deadly weapon is best for W-M1s, but they have to be really sneaky and go behind people to get the crits, though they cannot airblast that well, as 50 ammo, 4 airblasts in 200 ammo, the regular 20 ammo gives us: 10 airblasts. So it is a good weapon for begineers who have no intrest in airblasts, not for the begineers who only want frags, but the...OMFG, i just realised how badly i went off this subject...erm, let me rephrase for Pybros: Don't use as less airblasts!

The deagreaser:
This isn't the best option, as even though the switch speed can be useful for destroying people with a "degreaser flare gun" combo, but the airblast penalty, though small, can reduce the total airblast capacity is 8, and it's damage penalty just screws it up, so i know the engie's dispenser can take the ammo penalty away, but when away from the dispenser...etc.

The phlogistinator:
No...just not a pybro weapon, damage is good, but the cost of airblast is too much, no more words on this story...

This is still an early guide, so it isn't the best, but i think my guides will be much better now, as i have a editor, someone to help me with these, so my efforts don't run out as quickly, as you could tell from the secondaries, he took over the primaries, my editor is:
"The Amazing Diffman!"
Note From The Amazing Diffman
I would just like to thank sentrybuster is spy for allowing me to contribute to this guide and all though I didnt do that much i still really enjoyed working with him. Ill hand the ''mic'' back to sentry now.
Anyway, say what you think in the comments and taa raa (P.S: i would reccomend for loadouts: Stock Flamethrower, Shotgun and the Homewrecker)
(PP.s: sorry this took a while, but diff was way camping for a while)
MMMMMPH
(WAIT!)
MMMph mmmph
(I just wanted to say goodbye :D)