It goes without saying that competition in the NFL is fierce. Any edge, even a small one, will be pursued if it means the difference between a win or a loss.
Finding that edge can lead to interesting, and sometimes unique, drills. The Dallas Cowboys, for example, are requiring their receivers to carry bricks from one end of the end zone to the other to build their hand strength. Washington Redskins safety Josh Norman is wearing a weighted vest in practice in hopes he will feel lighter, and therefore be faster, in games.
Several years ago, the Kansas City Chiefs had a training-camp drill in which a receiver would get into a port-a-potty stationed near the practice field, shut the door behind him and take a seat.