Huo-Long Heater

The heater is a ranged weapon for the heavy that begins to appear in chests from the beginning and can be found in all other sources as well beginning in the forest. The heater is exactly the same as the minigun except that it occasionally shoots out a small ball of flame in a random direction that can set enemies on fire and that as of 4.6 it also shoots in a wave pattern like the minigunPP. This secondary effect works even if the heater is out of ammo.

Strategy
Mandarbmax says: The heater is almost strictly superior to the minigun, but not by much, if you find a minigun with more upgrade slots, use that instead.