It seems that, barring one's alt-mode, it is the weapons that become the most distinctive characteristic of a mech. No one seems to want just the same old plasma gun, and who can blame us? These are incredibly advanced beings we're playing, who can transform their bodies into literally anything our imagination can explain away. Of course, once you got your uber-cool Destroyer-of-Worlds mech, along come the Mods to ruin your fun, because, y'know, that's all we do. No, really.
So, in the hopes of looking less like a boogeyman and more like the player I also am, and since I seem to be one of the nitpickiest about Weapons Systems, I'd like to give you some suggestions and ideas when getting started creating your mech's weapons.
A. 1 Melee/2 Missile OR 1 Missile/2 Melee.
This is an excellent ground rule, because it creates a measure of balance. Yes, your mech might be a great sniper, or a helluva frontline fighter, but this also means that even if caught in a battlefield that doesn't benefit them, they're not at an impossible disadvantage, which would make little sense given how long they've been fighting. You have access to three weapons - TRY TO USE THEM ALL. And don't try to negotiate for 3 Melee or 3 Missile, you will be crippling your character very badly.
B. Damage.
Heavy Damage to Light Armor >>> Medium Damage to Medium Armor >>> Light Damage to Heavy Armor.
Medium Damage to Light Armor >>> Light Damage to Medium Armor >>> No Damage
Light Damage to Light Armor >>> No Damage >>> Enemy laughs at you
Take your standard energy gun, good ol' staple from the sci-fi world. Wielded by an average mech, this weapon tends to do Medium Damage (MD) to Medium Armor (MA). Now go from there, and keep the weapons balanced. It is a good idea to start from the point where two of your weapons do MD to MA, and one does Light Damage (LD) to MA, though it's perfectly possible to have MD all across the spectrum. If one of your weapons does Heavy Damage (HD) to MA, however, either handicap the weapon (long recharge, very scarce ammo, long regeneration), or handicap the other weapons.
C1. MELEE: Close-Quarters-Combat (CQC)
It's perfectly possible for a mech to have barehanded fighting as a Melee Weapon. Decepticons are built sharp, spiky, fanged and taloned, after all. It wouldn't be entirely unlikely for an Autobot to specialize in unarmed combat, just in case they are caught weaponless in a bad situation - after all, ammo runs out, energy cells get depleted, missiles don't exactly come back once fired. What's important is that you MENTION it. Does your mech have fists the size of small moons? Does s/he, like Barricade, have a heavily augmented grip, turning him/her into the mech equivalent of an anaconda? Does s/he specialize in joints? Quick strikes? Grappling? Punching lights out?
C2. MELEE: Bladed, blunt and exotic weapons.
We have… just about everything in S:E at this point in regards to Melee Weapons. Blades, both energy and metal; clubs, maces and hammers; there's even a few polearms about, and even a couple of whips and whip-like weapons (I think there's even shuriken). This kind of weapon has obvious disadvantages to a gun, but one HUGE advantage over them: THEY STAY. They don't run out of ammo. Unless they're energy-powered, they don't run out of power. They, for the most part, are too resilient to be broken, and when they are flimsy they can be easily replaced. On the other hand, the damage they do is greatly dependent on the mech wielding them. Whips and daggers, for example, do LD to LA as a norm; they're meant to slip in past armor seams or immobilize, not damage. Polearms are excellent defensive weapons in melee combat, as well as offensive, and they can easily do LD and even MD on MA when wielded by the average mech. A sword is likely to do MD to MA even in the hands of a light mech, as it's nothing but one big piece of OW!, and anyone swinging a war hammer or a spiked mace can probably do HD to MA; those things are heavy on their own, and have very nasty points.
As a note, it's always good to specify the Armor level of your weapon, because if you're swinging a whip, a polearm, or even a sword at someone, there's a good chance they're going to swing BACK at it and try to remove it from the equation.
C3. MELEE: Add-On effects.
One thing that seems to go unnoticed when creating a Melee weapon is how much nastier than nasty it can be made by the simple addition of heat, electricity, and all kind of sundry effects. It's not the same, after all, to cut a piece of butter with a knife, as it is if you first heat that knife up to cherry-red temperatures. Hitting someone with a war hammer isn't quite the same as hitting them with a hammer that carries a concussion effect (a highly concentrated shockwave, bit like a sonic boom in a can), knocking them back or knocking them out (if they're light enough). Stabbing someone with a stiletto carrying a pain-inducing load of nanites, or swatting someone with an electrically-charged tonfa, will get their attention a helluva lot faster than if you just bat at them with a piece of steel pipe. However, adding an effect also means the weapon damage go up, so you might have to handicap your other weapons accordingly. All things in balance.
. Missiles (also applies to mines and other large bits of explosive substances)
Ahhh, good ol' missiles. More often than not carried by jets, helicopters, and really ill-tempered Saleen police impersonators. Missiles are the Seeker's signature weapon (you can hardly find any of their specs lacking the things) and one of the deadliest things out there (HD to LA starting). Provided they can hit you. As the standard missile moves at anywhere between Mach 3 and Mach 5, while most jets (barring the most lickable and altogether too-big-for-approval Blackbird) max out around Mach 2-3, it becomes a matter of how good a shot you are. Enter the targeting systems. There are currently 6 commonly targeting technologies to be found in our planet (and 1 S:E exclusive offshoot), most of which can be adapted to the S:E TFs without any problem at all.
Pre-programmed: The oldest of the lot, but still a good ol' workhorse, pre-programming a missile means giving it a set of fixed coordinates (usually the other guy's base of operations) and sending it on its merry way. There's no flexibility to this attack, but unless it gets shot out of the air, there's a better than good chance the missile will do its job.
Laser-guidance: Oldie-but-goodie, laser-guidance is exactly that: point a laser, the missile follows it. There's a number of variants to it (like the laser tagging seen in the movie, which is meant to aid a triangulation targeting computer), but in the end it boils down to that one beam of light. It's slightly more flexible than pre-programming, since shifting the laser shifts the target, but it does require line-of-sight, which can be a problem if the other guy doesn't, you know, WANT you to shoot him with missiles.
Heat-seeking/Spark-seeking: The current reigning champion and its S:E bastard child, these are exactly what they sound like, a targeting system that locks onto a particular source of energy, being it heat or the particular radiation given off by a Spark. They can maneuver to follow their target without any input from their source, but they can be fooled by flares (in both cases).
IFF (Experimental): Identification-Friend-or-Foe is an experimental system in which a missile sends an automatic signal to any vehicle, and gets an equally automatic response from a beacon in said vehicle saying "I'm friendly". Lacking this response, the vehicle is assumed to be "unfriendly", and targeted. IFF, however, has seen little development because it would be prohibitively expensive to put beacons on every vehicle and every piece of equipment the army of whatever country does not want its own missiles to blow up, as well as requiring other targeting technologies for "unfriendly" vehicles.
Feature-seeking/Silhouette-seeking (Experimental): Both takes on the same principle, you might be more familiar with the second one from sci-fi: the capture and identification of an outline against a database of the same. This means no amount of flares will distract the missile from its target, but transforming might. Feature-seeking, on the other hand, relies on distinctive bits and pieces (the Grippen's nose-wings, the Sukhoi's distinctive "bump" canopy, the needlenose of some MiGs, and the such), rather than a complete whole, so they are a hell of a lot harder to fool even if their target transforms.
Note that missiles are exceedingly time-consuming to regenerate, as befits such a powerful weapon.
E. Energy Guns VS Solid Ammunition Guns (aka, what other nasty stuff to do to the other guy).
It's actually somewhat rare to see solid ammunition guns unless they belong to the alt-mode the mech is taking, which is a sad but understandable thing. Energy guns, after all, depend on the mech's own energy to run or on solar power, so they can be fired pretty much forever. Ammo runs out, yes, but it also comes in a wondrous variety. As I'm sure someone in Mission City must've said at some point, thank goodness for Sabot ammunition. A few of the effects you could attach to ammunition weapons go as follows:
Armor-piercing: oldie-but-goodie, humans have been using APs for almost as long as there's been armored vehicles on the battlefield, and I don't imagine the TFs are all that different, considering they're born armored. I would say this is almost a given, and there's plenty of ways to add this effect: superheated rounds and spent uranium (or an equivalent thereof), for example.
Explosive/Shrapnel: another true-and-tried goodie, an explosive round detonates on contact (think grenade). You'll notice I don't mention hydrostatic because that's a condition dependent on being mostly water, not mostly metal.
Incendiary/Acid: even if you're firing on a HA opponent and your bullets cannot penetrate, a bullet that explodes into acid or a gelatinous fire will still startle the living daylights out of them, not to mention potentially splash and seep past the armor. Liquid pellets aren't good for immediate damage, but their greatest advantage is that they STAY, needing to be washed off, or the armor where they impacted discarded, to avoid further damage.
F. Nozzle weapons.
There are a few mechs who use weapons that rely solely on liquids - water, incendiary compounds, acids or even a cryogenic agent. For the most part, they are limited by range and damage (though one of them uses it as a knockback weapon, not necessarily to hurt, which is exceptionally clever), since there's only so far the fluid can be propelled while retaining its properties to either burn or chill. In these weapons, the damage to the armor is really incidental, and rarely goes beyond LD to LA. What matters is what happens when it seeps underneath it. Liquid agents can go where ammunition cannot, which is their greatest advantage, but also their biggest problem: they can easily be washed off and neutralized, unless directly injected into a fluid line (fuel, coolant, lubrication, etc.) Even in the latter case, purging that system of its contents can neutralize the damage. Always be very careful to specify the effects of any such weapon in great detail, so that the Mods can have plenty of information to start with when reviewing a character. And mind that such weapons need a fuel tank that can run out awfully fast.
G. Hacking.
There is at least two hackers of note in the S:E world,
probably more that I may not be aware of. It is their specialty to bypass a mech's firewalls (his immune systems) and give or take from the data they find
in there. Virus are a dangerous, deadly weapon, not a spur of the moment thing, nor is the ability to use them as a weapon something someone can just up and
pick up. Frenzy is one of the Elite because he's the BEST at it, being able to both hack and fight (and having the equipment to do so). Blueberry makes it
not only her job, but her passion, but she carries no weapons barring her hacking equipment. Respect their skill (be afraid of it, actually 
) and if you
want to join them, make sure you carefully map out how you're going to handle someone who uses a weapon that has as high a level of damage as it does of
failing altogether.
H. No-damage weapons and shields.
It's entirely possible to have a character with weapons that won't harm their opponent, but somehow incapacitate him. I have a medic who carries an EM gun, normally used to numb a patient's pain away, but which can be used as a concussive cannon of sorts, as well as a diamagnetic gun that makes it damn near impossible to move or transform a limb. There's a number of shields, both physical and energy-based, all of which can be used as purely defensive weapons. Don't let yourself become limited on thinking a "weapon" must by definition do damage. IMAGINE!
