Thanks goes to Illidan for proofing/contributing to bits of this.
80mm heavy cannons: These are fixed. They hurt. They can knock smaller things around, too, though don't count on them to have a magic "toss smaller Zoids" effect or anything like that.
60mm cannon: Point and shoot, but remember it can turn some.
50mm mortars: Two things to remember here. 1) Lead your shots. That is, shoot where your opponent is going, not where they are now. 2) Splash will hurt you (and teammates), so do not fire these point blank unless they will hurt your opponent more than you.
Tail missiles: Don't turn to fire these in most cases. The best use for them is getting things off your tail, so save them for that. If someone is circling you, you can try stopping your turn-to-shoot and whirling the other way, dumbfiring the missiles into their path.
Tail itself: The club is obvious. Go into melee lashing it. It makes a nice deterrent to things going for your arse, and can sometimes psych someone into going more to your front and thus your guns.
Array: These are your pretty fins, aka "why you should never jump on a Gorhecks' back"...they're not truly sharp, but they're not nice to land on either. You get targeting and nice radar, which won't find a true stealth Zoid but can be shared with teammates. You also get jamming within a 200 meter radius, which is occasionally handy. In a 1 versus 1, turn both on from the start - if you have teammates, be sure not to use the jamming until they're out of range unless it'll hurt someone else more.
Tri-Barrel Grenade Launcher: The bio says a Gorhecks' weakness is its sides, but I disagree: a bigger threat to an unmodded Gorhecks is something that has the sense to get behind it and not close to melee, instead scooting about and shooting it in the arse...at least at your side you have a better chance of turning to meet them. This makes things trying that explode. Enough said. I wouldn't turn to use it otherwise - why give something the chance to get behind you? Your front guns are for offense, this is for defense.
Other mods are more icing on the explodey cake and very obvious. Vulcans and the Trample Unit shoot things, missiles lock and fire. Just don't shoot down your own missiles with all the automatic weaponry on a fully modded Hecks: lead your fire away from them or cut the spinny stuff (it depends on the judge how much you'll need to do - you can always ask). A Gorhecks that stops shooting entirely beyond illegal targets/teammates in the way is generally a dead Gorhecks.
In a team battle, you can lead opponents into others' fire, their blades, et cetera: while they're busy going "oh fuck, Gorhecks", they may not be able to evade the Glow Fox skipping in for their side. Your teammates can do the same for you - if your opponent is busy running from said Fox or your teammates can pin them, you have free reign to blow them to hell and back.
Aside from shooting things, remember: you are a tank. But you are not a Horn. You're not as insanely armored, but you can move pretty decently for a gun-oriented Zoid. While you won't be winning any cornering awards, you can scoot about and turn faster than some. Push every inch of mobility you can out of your little boxhecks. Keep moving, spread out damage, piss people off by leading their shots into your more armored bits instead of your sides. The more you make them work to target you, the more you can shoot them (though remember that the more you move, the less accurate your shots will be). I say this a lot, but it's key to staying alive.
The other way a Gorhecks really shines? TEAM BATTLES. It is what they were born for.
A Gorhecks on the field, especially modded, leaves the opposing team with two choices: Attempt properly to kill this thing, or go for its teammates while getting blasted.
You have armor enough to take scattered/half-hearted attempts at killing you so long as you keep alert and moving, so if your opponents try to get away with picking at you (or better still, ignoring you for the first round), shoot them. Shoot them good. Have your teammates draw their attention and lead vulnerable bits of enemy Zoids right into your firing arc.
If you're tag-teamed by people who fear you, work to turn it into a chance for your teammates to counterattack. A Zoid gnawing on your side is open to being shot by others, open to being (carefully) stabbed. A Zoid dancing at your rear is going to be focused on you not getting round to shoot it, not your teammate making to pounce on its ass. Coordinate with others so they don't hit you - make your Gorhecks' sacrifice count by turning it into bait for a trap.
When something on the opposing team stops moving, for any reason, it might as well have hung a "SHOOT ME" sign 'round its neck. Capitalize on this. It's a nice way to scare things out of using weapons that require lockdown - if necessary, you often have the sheer firepower to forcibly turn a CPC into explosions of the sort your opponent does NOT want.
The spots you will have the most trouble guarding, especially sans mods, are your rear and sides. Sides are obvious targets and thus more often attacked, but you have very little to defend your arse from a smart opponent once the missiles are gone, and an opponent there means a lot farther to turn than one trying to pick on your sides.
Do everything you can to keep them away, or at the least lure them into melee where you have a chance at hitting them with the tail or getting them to do something foolish. Make them FIGHT to get where you don't want them. Move unpredictably, push yourself to speed and flailturn around to lob tail missiles or get them in your forward arc for a bit. Use your fins and bodychecks to discourage melee of the sort you don't want - and again, keep the tail lashing. Scare people away from your rear entirely, so they don't get the idea to stay there and shoot.
Your top speed may seem an issue at a glance, but it's not a horrible one. In most situations, you're not going to be running so much as scuttling about, something you can do pretty well at 120 kph. I like maneuverability and speed, and I get along with Bitey just fine.
For starters, rush your opponent. Yes, rush. Give them less time to react than they think they have. Someone expecting an easy squish and being met with blazing guns and stubby ramming speed may well back off: if you can shake them up or get them to skitter around instead of coming in for the kill, it's more time for you to shoot. Swish your tail about, both to hit things that get in its way and to spook them.
Work to come in at an angle that makes it hard for opponents to easily pointify you or get an impact cannon into you - a Gorhecks has armor, but it's still a level three, and it can't take obscene punishment. Get close to a limb or other vulnerable spot and pump it full of lead (no mortars if'n there's more armor on them than you). If you can cling and are sure this won't bring pain, do so with all the glomp your legs can muster and try to take off the leg. This is wonderfully effective when your opponent doesn't have blades or guns that can hit regions around their ankles, but is not sensible to try on, say, a Blade Liger's front half.
Really, a Gorhecks' best bet in melee is being unpredictable and shooting lots. If you can derail fancy attacks and reposition yourself so no single bit of you takes all the hurting, you can last quite some time. The harder you make yourself to kill, the better chance you stand of taking out your opponent with sheer firepower while they're trying to claw/stomp you.
In a team fight, have people keep you out of melee you can't handle. Work together with someone speedier and pointier to entrap things moving in for the kill on you, so they're forced to choose between maul the Gorhecks and get stabbed and attack the speedy thing and get shot. I've said it before: coordination is key to a successful team fight in a Gorhecks.
Ligers, especially ones with enough firepower to do decent damage, are quite good at this. I've fought alongside Houndsoldiers and Foxes too.
Beyond that, I haven't done much. Yet.