While it hasn't evolved much from the original, Robokill 2 is a very nice singular dual-stick shooter (until it becomes monotonous and repetitive, which might be the true flaw of the game, since this exhaustion probably sets in kinda soon). Fight near-endlessly, with a little bit of keycard collection and a nice inventory/robot customization system.
And it does the fighting well, with a reasonable variety of enemies and AI behaviour (those ambushing dudes who shoot past cover can actually be tricky to land hits on, and occasionally human-like in their evasion), plus some small peripheral considerations (crates to hide behind or to destroy to flush out the enemy, rolling exploding barrels, and other small terrain elements, plus those durned ledges to overstep and plummet past).
The only thing I'd like to see (besides the engrossing narrative that is sure to become a standard feature of DSSs any day now
) would be a simple character (robot) progression mechanic, with a few skills/permanent mods to complement the nice inventory system. Stuff like shield strength/damage mitigation, movement speed, additional damage, possibly stuff more exotic (damage/projectile reflection, stun effect), and perhaps even silly cash boosters. Etc.