Multiguns (MGs) are built by engineers using the "_special2" command.
MG's require CELL ammo to build.
They must be upgraded by having another class TOUCH THE GUN.

Scout = Displacer
Demoman = Grenade Launcher
Pyro = Flamegun
Sniper = Laser-guided rocket launcher
Medic = Biocannon
HWGuy = Exploding Crowbar Gun
Spy = Tesla Coil
Soldier = Rocket Launcher

Once an MG is upgraded, it stays that way until destroyed.
You cannot heal MGs. They do not require ammo.
MGS are damaged by friendly fire! (except hits by a wrench).

Inert MGs can be CAPTURED by the enemy team. Make sure
your MG is upgraded before the enemy can touch it!