A friend recently ran an experimental game about mechs blowing each other the fuck up. We used a simple system he had cobbled together out of various parts, with the combat system being entirely bespoke. The primary motivation for the game was the guys love of Steel Battalion, something I can support. Seriously, go read about this game before going on, it's pretty badass.
So, the main divergence point with Steel Battalion is the agility of your mechs (known as Vertical Tanks in-universe) as well as the targeting systems available. Thanks to computer assisted aiming for almost all weapons, each weapon discharge is assumed to hit unless the target takes preventative measures, which for most weapons involves a dodge move to the left/right. Whilst the VT is pretty mobile, dodging like this strains the system, meaning you can only do it every so often (we worked it as once per turn rotation) without specialist systems or skills.
Seeing as we were playing as a routine merc. group, we only had the most basic mechs available to us, which led to a feeling of our mechs simultaneously durable and fragile - you can avoid being hit, but if you get cornered or focused, you are going to quickly explode horribly. Furthermore, the mech is not your character - the pilot inside is getting the feedback of shots impacting. This was represented by addition 'force' damage dice, which represented the chance of powerful weapons to both throw the pilot around or knock a mech flat - a dangerous position. Being on the floor means no dodging, meaning you get pinged by shots over and over.
The other important thing to note about combat in this universe is the importance in ranging - most weapons have a minimum range they can't be used within, the rounds pinging uselessly off armour. The majority of combat relies on you positioning effectively between your minimum and maximum ranges whilst trying to spoil the opponents ranges.
To give the system a whirl, we were tasked with conducting an ambush on a small convoy consisting of 3 non-combatant carriers and 2 medium-weight enemies, known as Scarefaces. Our motley crew consisted of myself in a heavy-weight mech I had kitted out almost entirely to smash into others with a close-combat weapon, a pair of long-range firepower mechs and an EWAR/Spotter role light mech who was tasked with guarding the heavy hitters.
Unfortunately, we got spotted in our ambush and this led to a messy engagement. Thanks to the inherent clumsiness of a heavyweight mech, I fell flat on my face attempting to close distance, getting a rifle slug in my side for the trouble. Our ranged section was far more effective, the initial barrage of howitzer shells and rifle fire near-flattening one of our opponents and damaging the other. The said flattened enemy spent their turn picking themselves up, the pilot inside panicking and losing an action for it.
In the next turn rotation, I spent my entire turn attempting (and eventually succeeding) in righting my machine, whilst the already damaged target was finished off with another round of pummelling. The remaining target attempted to retaliate against the howitzer-user, who was saved by the EWAR mech firing down a locked-on missile.
I finally redeemed myself by tearing open the remaining armed enemy, removing the cockpit from it's rightful place, leaving plenty of salvageable material. The small carrier mechs were now attempting to flee. One of them was 'convinced' to surrender, whilst the other two were destroyed. The first took a burst of machine-gun fire into the back, scoring hits into the gas-regulator systems, causing toxic fumes to gas out the pilot. This was only possible due to reduced armour facing in the back, giving a small chance of hitting vitals. The remaining carrier was flattened entirely by the ranged team and their sustained fire.
Overall, we all had a blast with this, though we will probably use a miniature grid in future for distancing purposes. Some of the stuff I didn't cover here includes the perks you were given access to, which enabled extra options within combat. All of us look forwards to playing out more of this system, as well as refining it as time goes by.