Warframe

Does this count? I've got a +multishot +fire rate -(100%)damage tetra riven I use with mirage to terrorize my friends while contributing nothing to the mission

I've been having a lot of fun with Dual Toxocyst Incarnon on Zephyr specifically. Her augment Airburst Rounds provides base damage, so it frees up the gun Arcane slot away from Merciless/Dexterity/Deadhead. So in the Arcane slot I put Cascadia Overcharge for extra crit chance while Overshields are active. Her 3 generally protects the Overshields and guarantees she can maintain them. She also gets another crit chance boost from her passive whenever her feet aren't on the ground, and being up in the air aim gliding above enemies gives easy access to headshots, plus the grouping from her 2 helps the Dual Toxo's richochet. Just feels all round great, very fun to play

My favourite combo is the "Rolling Gunslinger" Mesa, taking the power of Mesa's Waltz to it's extreme. The required ingredients are 2 Parkour Velocity Archon Shards (or 1 Tauforged, which is what I prefer) and a mod you never see used, Amalgam Barrel Diffusion (put it on your secondary, not Regulators). With all things combined, Mesa turns from the turret frame she's known for into one of the most mobile killing machine frames in the game, rivalling even Titania. Once you get used to how much forward momentum her roll gives, you can traverse all but the most maze-like tilesets without ever turning Peacemaker off, shooting everything that moves all the way to extraction.

Besides the obvious so called "weapon platforms" I think my fav specific combo is Trinity with a gas paris prime incarnon. Gas can't do much against armour and Trinity has an armour strip on her link. The problem is the link strips only 3 enemy so regular aoe weapons (that can't kill armoured enemies) are able to kill only 3 enemies per shot. Yet the gas clouds persist after the shot so you have that satisfying chain reaction of sorts.

Is that the best build I've ever played? Not really. Can I do half an hour sp survival using it? I sure can and it's almost chill (except ridiculously short duration of Trinity's abilities).

As to the weapon platforms - I quite like nourish wisp, can slap any decent weapon and it'll become a lot better, roar hildryn is just absurd with full strip and double damage from roar.

One very effective pairing I like to use is Zephyr with the Akarius. (I'd use the Epitaph instead if I had it)

Zephyr's 2 clumps enemies together, which is ideal for AoE weapons, and then the Airburst Rounds augment grants tons of damage to your secondary weapon.

I usually like to mod pistols with high base fire rate with even more fire rate. Arcane Pistoleer is kind of a requirement, and a Saryn focused around buffing weapons or Harrow with Lasting Covenant will generally go the furthest.
https://www.youtube.com/watch?v=INJDeUrMQYM

It's an oldie but a goldie - my favorite synergy is Nekros, Despoil, Equilibrium, Health Conversion.

I wish other frames had such unique interactions as well - a core game concept like health orbs, a warframe ability and augment that causes ability to run off health, getting more armor by getting more orbs and then using a weird equilibrium interaction so you can pick up even more health orbs even when you're already full, while generating tons of them with despair... it's so weird and unexpected and yet it just works off each other so well 😁 it all just comes together in a way

Static Discharge and the Prova Vandal, which is dispo FIVE, are a complete blessing for Kullervo. With the Mecha set on him AND Contagious Curse, he goes from a single target muderer to a triple dipping map killer.

Xaku really, really wants a Sword and Shield weapon, preferably the Tenet Agendus because it has the largest parry angle of any shield, no matter how big Argo and Vel look. Xaku just runs around in Block Combo, building up Adaptation while blocking 100% of damage from the front, and thanks to Grasp of Lohk, nothing behind him is alive. Add Arcane Phantasm for zippiness.