Nice question – I’m also a 3D asset creator, mainly environments, and I constantly ask devs the same thing.
From what I see, the assets that get used the most are not the “coolest” ones, but the boring, modular building blocks that let you actually build levels:
Environment kits: walls, floors, stairs, railings, fences, doors, windows, roofs.
Set dressing props in small / medium / large groups: crates, boxes, barrels, furniture, cables, debris – designed so they can be clustered into readable shapes instead of random noise.
Utility / gameplay objects: switches, gates, terminals, loot containers, signposts – anything devs can hook up to their scripts.
Weapons are fun, but that market is very crowded.