All Hail Our Lady of Aimbot!

A general-purpose [Mesa] build based on 300 mission hours playing her specifically and endless tinkering. She can swagger through Steel Path, Open World bounties, Railjack and everything else in the game with perfect ease. You'll still want at least a solid Titania or Wukong for speedruns, Volt for Eidolons and some Focus farming frames like Saryn/Mirage, but this quality-of-life build is what you need to sleepwalk through the vast majority of the game.

This is an endgame QoL build. Advice for earlier players: the Corrupted Mods ([Fleeting Expertise], [Narrow Minded], [Transient Fortitude]) are the key, so run Orokin Vaults until you've got all three. Primed Continuity is only necessary as a way to hit effective Efficiency cap (3.75/s Peacemaker Drain) with a 160/160 Duration/Efficiency setup, rather than 190% from Streamline (hardcapped at 175%). Flow/Primed Flow are "nice to have" non-essentials for squatting Defense objectives.

Umbral Forma can be hard to come by at first: [Vitality] + [Steel Fiber] + [Fast Deflection] until then, don't waste Endo on the last two ranks of the first two.

Armament: pair with this 1.2M DPS Regulators Crit-Heat build (Forma-compatible with this 950K DPS Armor Strip build), and your choice of weapons. You'll almost never use your ranged weapons except on Arbitration Drones and destructible mission objectives, so you can use whatever you like here. Personally I go with Daikyu for the 3% lifesteal Amalgam Daikyu Target Acquired mod + Sepfahn Hybrid Stat Stick w/ Exodia Brave to both heal and charge. [Sporelacer] for killing the aforementioned drones & objectives...in theory you could use it to prime targets with Status but in practice... this is [Mesa]. You hit 4, you look in the general direction of the things you want dead and they die. Cascadia Flare for Secondary Arcane if you're running the Regulator Heat build, or consider Cascadia Overcharge.

Helminth Roar vs Eclipse: I've gone Roar for the status proc double-dipping and buffing teammates - we're already at Efficiency hardcap so the consumption barely applies. I do use Eclipse for my Index build out of energy economy/availability concerns.

Flexibility: if you want a little more power you can drop [Primed Sure Footed] for Power Drift but this build absolutely demolishes Steel Path Eximus already and knockdown sucks.

There's probably a (non-Forma-compatible) shield-gating version of this for pushing into extremely high levels, but outside Zariman Range is useless for [Mesa] and Duration only matters insofar as its loss might impact Efficiency, so the Augur mod synergy just isn't there for that. For pushing into higher level Steel Path or survivability in general we swap [Narrow Minded] for [Adaptation] and [Primed Flow] for [Streamline] to compensate.

For Index we reshuffle things a bit: raw lethality and Magnetic/Knockdown immunity take a partial backseat to Radar and Arcane Energize. This is also the lone build where I use Eclipse rather than Roar for energy economy reasons, and [Mesa's Waltz] for line of sight dithering.

For Zariman bounties we Helminth Golden Instinct, and then slot Augur Reach and Augur Message over Narrow Minded and Transient Fortitude - this gives us a 260m range on GI, allowing you to check it periodically over the course of the mission and drop Parallax Air Support once it pings on something. It's also nice to not have to toggle 4 as often to reset Peacemaker FOV during Void Armageddon.

How to play: bullet jump around a corner or straight up into the air, hit 4, swish your mouse around while holding fire. Watch with smug satisfaction as everything dies, repeat as needed.