So where are your fixes to: it's been vitally important that the weapons in the game are fun not just to use, but to play against.
the Sticky Bomb Launcher
the Mini-Sentry (Gunslinger)
There is no fun fighting any of these as they are easy to use, but hard to deal with.
Shoot stickies in general direction of enemy, detonate, profit! That's how this thing works, needs neither aim or skill, but does the most damage. Really, why give the weapon with most control the most damage (crit does 300+ damage) and highest ammo count (of a weapon with reload)?
Fun and easy to use, hard to deal with.
Shoot fire for a split second to get guaranteed crit with Flare Gun or Axtinguisher. Before you even know you are on fire you get killed in one hit. The fast weapon switch practically means the Pyro can use all 3 weapons at once. The only safe way to avoid this is being Pyro yourself. Also the damage penalty to fire is completly pointless as nobody who uses it uses the fire for damage.
Fun to use as you can choose weapons faster that everyone, no fun to get killed by.
A small target that never misses a shot that is built in a very short time. Many times these things come out of nowhere and before you even realize what is shooting you and from where, you are dead or badly injured as they have quite an impressive range for these small things, and they shoot very fast.