This is a bug that have been occured since month now and that is still persistant throught the updates and method to make it work again.
The problem is simple : any gun or weapon meant to be used by my character by holding it and shooting/throwing it once placed in the weapon hot bar(confetti gun, bubble gun, throwing knife, ect...) end to never appear in his hand despite the item being placed in one of the 8 emplacements, even when pressing the associated button afterwards.
This is happening of course everywhere where "weapons" are allowed, such as the Plaza on the outside or my every own Condo.
I already tried to uninstall/install the game, let steam verify the integrity of the game cache, removing/replace the weapon in his slot of course, and also erasing the whole content of the Steam\steamapps\common\Tower Unite\Tower\ClientPlayerData2 file while having steam cloud disabled so it could reset everything, but nothing works, my character still refuse to hold anything.
However, items that goes in the wearable hotbar perfectly works, jet pack as pets.