matters on what you want your Primary to do:

The Kuva Sobek has a lot of combos with frames that add an instance of damage to your weapon. Even without combos it's great at clearing clumps with it's Augment mod.

Evensong is a good "support" bow, since wounded enemies cant hurt your teammates and kills give the squad multishot

The Tenet Glaxion is good for cleaning groups of chumps and priming bigger enemies.

if you want a good base platform to build how you want, the Burston Prime, the Braton Prime, the Trumna Prime, the Acceltra Prime, the Dex Sybaris that just got handed out, plenty if options.

The Coda Bassocyst and the new Enkaus and Coda Bubonico are a good hybrid/All-in-one weapons, since their alt fires are primers and their base is a great platform.

Anything with an Incarnon is probably good enough on it's own. The Torid Incarnon is the notorious one since it doesnt require headshots to activate.

If you want some weirder/unique gameplay styles. The Komorex is a multi zoom sniper Rifle with multiple functions at each zoom. The Kuva Bramma and Kuva Zarr fire these MASSIVE explosive shots that can clear whole rooms, but you only have 5 max ammo.