Thank you for the progress report, very cool! I like the digestible little details about how you made some of the game systems work. And I don't know if you're aware, but MASER is an acronym, similar to LASER:https://en.wikipedia.org/wiki/Maser , both being devices that produce coherent beams of Light, with maser being just a type of laser that works in the Microwave range! In real life, it would work like a laser, rather than the Tesla coil-like electrical arc thrower shown here.
That brings me to my 1st weapon suggestion, a high powered microwave: An HPM is to a maser what a floodlight is to a laser, and it's the technology behind what is usually depicted as "EMP" in fiction. It should be capable of downing drones and missiles, messing with computer systems and comms, and even stunning or killing organic nervous systems at very close range. It should probably be as noisy as a laser, but invisible to regular optics. Very, very visible to certain Radars, though. Bonus: HPMs really do use satellite dish or radar-shaped projectors!
My 2nd, cooler suggestion, is the gyrojet: https://en.wikipedia.org/wiki/Gyrojet. The projectiles would start out slow and harmless, and accelerate, gaining damage and penetration power as they travel. Kinda like the railgun, but they would reward the player with a better rate of fire for requiring positioning away from obstacles that would block the rocket before it gained enough speed. Kinda like the enemy LOSATs, actually, and similarly cold war-esque.
The 3rd suggestion is what basically everyone else mentioned: explodier indirect fire weapons! Though for something as martian (read: spindly) as a crawler, a mortar probably makes more sense than a howitzer. Martian mortars would also need less propellant than earth-based ones, so maybe they can be more over-engineered like the AMOS: https://en.wikipedia.org/wiki/AMOS, or a Sturmtiger?
An idea for yet another 20mm Autocanon: Hyper burst mode, based on yet more cold war era madness, in the form of the G11 or the AN-94: first few rounds after firing are fired almost simultaneously and very accurately, then it becomes regular auto-fire if the mouse button is still held.
Some thoughts about types of ammo:
Proximity-fused air-burst shells: for firing around pesky corners, and having to aim less. Maybe even make the shell automatically direct a shrapnel cone at the detected target? inspired by the XM25 CDTE and the M329 120mm shells.
HESH: Big damage and huge stagger, but needs to splat against hard targets for the explosion to actually do much! Maybe a version doped with shrapnel, even.
Toxic Gas: Would work like the smoke launcher (which I really like!) usually, but would damage over time and confuse organic targets or improperly sealed vehicles. Maybe even make a flamethrower-like gas or smoke projector?
Expanding sticky foam: to make puddles that slow down enemies, or to suffocate or even crush them if they get completely covered by direct fire. Arguably my most interesting idea here. Also to put out fires, if that ever becomes useful in some level!
All these ideas can be their own weapons, but I'm thinking about a weapon with a variable ammo mechanic. I'm especially thinking about the 120mm cannon, which I feel is the least useful weapon currently, by virtue of having a low rate of fire, bad penetration, and not enough damage to justify everything. Being an adaptable multi-tool with different shells could make it both more useful and more unique and interesting.
Finally: an assortment of lightning-inspired weapon ideas:
Electrolaser - ruler-straight lightning is a visual that always fascinated me, and in-game it could have the visual cool factor and damage profile of your new electric arc weapon without the tracking, but the fire - starting and hit-scan convenience of a laser without the infinite range.
Ball lightning launcher - we don't know what ball lightning actually is irl, so we can make up whatever! My idea is slow, floaty balls of plasma that automatically home in on targets made of steel before zapping/exploding them.
Thermic lance - A melee weapon, could work like a jousting lance: damage would be dependent on velocity at time of impact, though maybe it could also be used to slash, like the plasma whip. Unlike real thermic lances, this one could have its rod be unwound from a spool of wire to restore its length after every attack, with that being the "ammo" for the weapon.
Well these were all my ideas. Again, thank you for this game that's both beautifully pixelated and refreshingly arcadey!