The Imperium of Man isn't the only faction toting ECKS BAWKS HUEG guns to totalled the entire battlefield in one shot. The Squats themselves also manufacture their own family of FUCK OFF cannons. A few Squat weapons have been integrated into Imperial arms due to millennia of trade, but these are the ones used exclusively for Squats, by Squats.
Chthonian Mole Grenade Launcher
The Chthonian Mole Grenade Launcher is so named because its primary users are the Chthonian Beserks. Unlike the missile-like launchers of a Mole Launcher, the Mole Grenade Launcher as its name implies, is a grenade launcher with a special camera-system in the front of the barrel to act as possible laser designators. These weapons, like most Squat weapons are repurposed mining equipment that delivers subterranean explosives into the midst of enemy units, even if they are cowering out of sight.
Rules wise, their grenade launchers are 24" HunTR d6, S5 AP-2 d1, with Blast and you can target enemies that aren't visible to the bearer, and it gives the corresponding model an extra wound and attack. It also grants the Subterranean Explosives keyword. A 10 point option for your Beserks, this weapon suffers from the -1 to hit that indirect fire weapons do nowadays but gives you access to the incredibly powerful Subterranean Explosives stratagem.
Exo-Armour Grenade Launcher
Due to the environment they operate in, Squat Hearthguards often have a shoulder-mounted grenade launcher fixed-into their Exo-Armour to soften up the enemy's position before going in to tear them a new asshole. These snub-nosed grenade launchers lack the range of most grenade launchers, but that is okay given that the Hearthguards in general aren't the most shooty types of folks.
In terms of rules, this translates to an 18", HunTR D6, S4, AP-1, D1 Blast weapon. Not too shabby when it comes to dealing with those annoying pests like GEQs, but don't expect much against heavier opponents.
The actual cannon of the Thunder-Fire Cannon (Jeez, a bit of deja vu here?). The Thunder-Fire Cannon was the foremost first line of defense for the Squat homeworlds and possibly the second largest artillery right next to the Goliath Mega-Cannon. Seriously, it might be Epic, but those are fucking big guns capable of firing fucking big shells from quite a considerable (and fucking big) distance.
Just to give you an idea on how ridiculous Squat artillery is. The Thunder-Fire Cannon is a supporting artillery piece meant to provide backup for the Goliath Mega-Cannon. Oh yes, an artillery piece supporting a even BIGGER artillery piece.
As you can imagine, these things are triple-barrelled, kind of like the more mobile but smaller Dominus Triple Bombard. The Thunder-Fire Cannon in itself is always seen mounted as a static piece of artillery. So we ain't completely sure if it can be mounted on a mobile platform, although it wouldn't really surprise us granted that these are the Squats we are talking about here.
For the actual vehicle itself, see here.
A hilariously phallic weapon made by They-Who-Shall-Not-Be-Named. The Goliath Mega-Cannon, both the gun and the vehicle (Don't tell us why they decided to name both weapon and vehicle the same) is one of the largest artillery pieces ever known and fielded.
Basically each shell weighed several tons and was powerful enough to shatter entire fortifications and turn a fleet of Baneblades inside out. These motherfuckers were the Schwerer Gustav in all but name.
Curiously, the gun never really needed any shock absorbers to control the immense recoil. However it could be that the Goliath Mega-Cannon (The vehicle, not the gun) doesn't need one as the vehicle's own base is the gun's base.
The power of the Goliath means that each cannon fires its own barrage template. A Goliath attack is worth four barrage points plus the roll of a D6, giving a score between 5 and 10. The super heavy shells fired by the Goliath are so good at reducing fortifications to rubble that it ignores hit modifiers for cover altogether.
The Goliath lobs its shells high into the air to achieve its mammoth range, but it can't depress its barrel to hit a very close target. This means a Goliath can't shoot at targets closer than 50cm, so it has a min range of 50cm. They also don't have any self-defense secondary weapons so you need a few Thunder-Fire Cannons to offer cover support and picking off any units near the Goliath.
Of course, all of these rules are now outdated. But it is pretty cool to see the power it once had.
Not to be confused with the Thunderer Siege Tank of Leman Russ fame.
The Thunderer Cannon is a giant FUCKOFF cannon and one of the largest form of ordnance known on land. This cannon is one of the primary weapons of the Squat Colossus War Machine and the shells of which, is powerful enough to cause nearby mountains to suffer critical existence failure in the form of giant mud slides. Seriously, just look at that bore size and translate that to the size of the vehicle itself.
The Thunderer Cannon acts as a giant artillery gun meant to deal with squadrons of superheavies and Titans rather than infantry and tanks. This is due to the placement of the Thunderer as well as the fact that it is not mounted on a turret, suggesting that the entire superstructure of the Colossus' 'tower' is reinforced, so as to properly handle the ridiculous recoil of this big stick of death.
Because of its placement and function, it is likely that the Thunderer Cannon was the basis for the Behemoth Cannon.