Assault canon..300 armour...... there's not much more to say about this class. Need someone to block a corridor? trap a passing enemy in the flag room? He's your man. This class is perfect for newbies as there is not much more to do than find somewhere with a nice field of fire and just MOW the enemy down. Since TF 2.9 This dude has become deadly, earlier he was bad-ass-hurt but now he's carnage incarnate.

General tips

• Find a position where the enemy are not going to be able to outmanoeuvre you.
• Use your double barrel shotty when on the move.
• Set traps for the enemy. for example on "the rock" sit inside the wardens office and when an enemy enters the room move to the doorway to block it. Start up the chaingun and watch them frantically run around wondering what to do. For added laughs use this tactic in the muskrat flag room watching them panic and run into the lava :)
• Use your MIRV grenades. It very easy to give an enemy 1 choice and that is to die :) throw a MIRV into a smallish room and and stand in the only exit, start the assault cannon.. and have a suitable taunting bind along the lines of "GRENADE!!! RUN RUN RUN!!!" or "make your choice ...Muhahahahahahah ...". Look to the psychology page for more tips on psyching out the enemy.
• Stand in corners when playing on servers with "newgrens".

Offense
Forget it.. unless the flag is dropped most of the way home and you need somone to clear away enemies defending the dropped flag.

Defense
Be as close to ammo and armour as possible unless you have an engineer nearby to help you out.

This class is harder to place in a good defensive position than the other classes since you need to have a good fire corridor. Some good positions are on the top walkways watching over the lifts in well6. The HWGuy can be thought of as a moving sentry gun. As such he makes a good team member to a soldier as his full-auto firing can close a hole opened in the defense as the soldier is reloading.

Aliases and commands

Toggle noaim:
Us autoaim (noaim 0) if your target is close, if he's far away, turn off autoaim (noaim 1)
alias noaim1 "noaim 1; echo noaim_off; bind X noaim0" alias noaim0 "noaim 0; echo noaim_on; bind X noaim1" bind X "noaim1"

Class binds:
bind X "reload" This will reload your weapon.
bind X "ID" This will ID the player. and if he is friend or foe.
bind X "saveme" This will yell for a medic or an engineer.
bind X "inv" This will tell your inventory of grenades.
bind X "discard" This will drop stuff you don't need.

Other resources:
UKFN Tactics for HWGuys
TF Guide class strategy for HWGuys
OX [CE]'s HWGuy tips