I guess I'll do a little raffle series from time to time giving away one to three of a specific item in MvM that's particularly good to use.
First up's the Beggar's Bazooka.
True to its name, the Beggar's Bazooka is an economy launcher. With this bad-boy there's no need to up firing speed, since firing and reload speed effectively become equivalent when you just load one shot into it at a time. Any SerndSmorth watcher can tell you it's more efficient that way unless you're turning a corner. This allows you to get health on kill and damage upgrades much faster than if you used other launchers on the same map. Be sure to be near a Dispenser when you rush to deploy your banner, though--that'll be around the only time it can give you ammo due to the penalty.