Be able to grab something and hold on to it.

Questions & Answers
1

I am making a game where an integral part of it is that I would be able to pick up cubes and move them to different places, as well as grab ahold of a moving platform from the bottom so that I move with it. One of my ideas (actually the idea that I want), is to be able to make the cube sticky (by adding a joint when it collides), and then stcking it to the underside of the moving platform. However, I don't know how to hold an object in that way. I can't make it a child of the camera, because then when it moves the character and camera won't, but if I make my character be a child of the cube, then I can't move the cube. A javascript would be nice. Thanks in advance.

2

Parenting is the easiest way, but you said you cannot use that. Next would probably be simply setting the cubes position to be right in front of your character.

//PlayerController.js
private var pickedUpObj : Transform;

function Update () {

     //Add code for selecting an object.  The easiest way is probably Physics.OverlapSphere()

    pickedUpObj.position = transform.position + transform.forward;
    //Places the cube 1 unit in front of the player.

}

If your player is controlled by a Rigidbody, then you could add a FixedJoint to your cube and it will stick.