The Minigun (or "Sasha" as referred to by Sonic The Hedgehoge) is the Heavy's stock primary weapon. The Minigun has a black barrel which spins rapidly on fire/special attack key and a grip with a dark silver bullet holdier.
It deals 4-12 damage at long range, 12-30 damage at medium range and 32+ damage at close range per 1 ammo unit fired. 10 units of ammo are fired a second, which is able to kill any Overhealed class at point-blank range in 1 second. Each unit of ammo fires 4 bullets. Think of this weapon as a rapid fire Shotgun, as each individual pellet or bullet is weak, but when many are grouped together they are very strong at close range. Also, they both have extreme damage falloff making it only really useful at close range or medium-close range.
The TF2 Minigun is very similar to the TFC incarnation, but it has one difference; you can wind up the gun without firing by holding down the alt fire key. This is very useful for when you're defending and the point you're defending is frequently attacked. Instead of having to wind up the Minigun every time you spot an enemy, you can just hold down the alt fire key and mow down any incoming enemies without having to wind down when there's a lull in the fighting. It takes about 0.87 seconds to spin up the barrel, and you move at a speed of 47% while it's spun up. While spun up, the player cannot jump and if crouching, cannot move. They can however start the spinup in midair as the slower speed only affects the heavy on ground, making ambushing around corners a effective stragety.