@wheretheidivides you are describing a method of picking up items and storing them in an inventory. What I and the OP are looking for is a tutorial on picking a physical object up in game and being able to move that object about in the air and then place it in another location.
I have set up a FSM to do this but it has some problems that I can't seem to fix.
I think a fix for my FSM problem would be to find a way for the object I've picked up (and would be floating in mid air) to instantly drop to the floor is it touches any other object.
At the moment I can pick an object up and it becomes a child of the first person camera. I can then move the fist person controller around the game and the child object will float in front of the camera and move as the first person controller moves. I can drop the object too. BUT the problem is when it encounters either another rigid body (they both fly about) and/or it encounters any object that is not in the tag group I've set.
Also, if I drop the object close to a wall and then pick it up again, it will sometimes disappear through the wall.
I'm sure there is a way to achieve this but I can't find a solution.
Squarebite Inventory
If you want an out of the box solution, here is one with playmaker support. I have never used it.
https://www.assetstore.unity3d.com/en/#!/content/13203