This has been in the game forever, so please fix it. It's so annoying if you are in a hurry and just found a gun, but can't pick it up. No matter how many times I click RMB, the item won't move.

However, if the item is stackable, like bunch of ammo is laying on the ground and you split them with the other half going in your inventory and the other one staying in the vicinity, you can combine them and after that you can move that item.