Sitting and thinking about this, I realised most of my favourite frames essentially all buff weapons to the point that there are no “not powerful” weapons. Banshee, Nyx, Zephyr, Sevagoth, Frost, Limbo, Ivara.

Some of my standout niche or “hidden boss” weapons are:

• Basmu: the cooler Nukor. Has a lot of different elemental builds. Has a cool corr-cold-blast build due to its primary fire having split elements between direct electric and radial heat. I’m still playing around with getting a good altfire build.
• Staticor: has the niche of being fairly weak on paper, but with an absolutely phenomenal radius and fairly good status chance. I’ve been running it on Frost and it performs way ahead of what it “should” according to my spreadsheets, so I don’t know.
• Alternox: I don’t care what anyone says, I love running this on Gyre because of how good it looks. With a riven and a bit of love, it’s quite functional as a crowd clearer, range extender, and bubble popper.
• Sibear: kind of a bad reputation as the most meh incarnon, but even if that were so it’s in the context of incarnons. Still hits like a truck, high range, stacks slows, readily stacks large amounts of cold, and combo racking that would make any gunblade blush.
• Redeemer Prime: Melee Afflictions gave this one new life. I run it on Stealth Xata builds as a nuke weapon.
• Pathocyst: people sleep on this one. Has the highest raw damage of any glaive, so it’s a great Afflictions carrier or Duplicate nuker. Still playing with a Crescendo build for heavy blast spam.

And an honorable mention to the Kuva Karak. Has a niche as a mag/blast weapon with good hybrid stats. I’ve actually found it outperforms the Tenet Flux as a Blast carrier, which was surprising. Great with Nautilus since it stacks IPS quickly to refresh Cordon.