This is Sascha.
Chainguns are fashionable.
The heavy is not as simple as he looks. Sure, he might have a big head. He might speak mostly in monosyllables. But his gun sure does shoot out a lot of bullets. This class is often overlooked by players that don’t understand how to overcome his weaknesses to make him into an effective character. Heavies are far better when paired with a medic, as without one, they are terribly vulnerable to rockets and demoman grenades. With the release of the pyro achievement pack and the ensuing overpopulation of pyros, the heavy has proven himself as the most effective population control agent to cut down on the hordes of rubber-suited lunatics. The spin-up time of the minigun, the slow running speed, and the relatively low range of the heavy all make him a challenging class to play.
You should not be spinning up your minigun all the time. Not only does that make you very vulnerable to other players, it’s also extremely loud. Any pyro within earshot will be able to hear you spinning up, and will rush to ambush you when you turn a corner. Only start spinning up when you are confident that you will have multiple, close to medium range targets in your sights. If you turn a corner and see that you are outgunned, stop spinning up and run back to cover. If you keep shooting, there’s a good chance you won’t be able to make it back unless you have solid medic support. Likewise, you should try to avoid spinning up and shooting too much in an open area, as it makes you particularly vulnerable.
The heavy doesn’t need to aim his gun terribly accurately, as it has a very broad spread. Make medics priority targets, as you’ll be able to strike them with high precision and distance relative to the soldier, pyro and demoman. Gun for soldiers as well - particularly if you have a medic. Their slow speed makes them easy prey so long as you have healing support to path up the holes that their rockets punch in you. Be very careful when you’re in close quarters, as you’ll have little hope of surviving if a pyro jumps you. Keep a close eye on your ammo counter. Don’t waste it on opponents that you can’t hit reliably, or you might hear the dreaded “click-click-click” sound when you need your bullets most. The heavy is very ineffective with the shotgun, and you should only use it in very dire situations. His punch is very funny to use and watch, but it’s easily the worst melee attack in the game, so it should be used sparingly.