Note: The following tricks required an unpatched version of the game.
Throw the weapon that you want to duplicate. Before it hits the ground, press Up. Then, choose to drop the weapon that is equipped. Exit out of the menu and pick up both items. Repeat this as many times as desired. Sell them for easy money.
Hold [Throw] with the weapon you want to duplicate, then hold Y + RT.
When using the "Duplicate weapons" glitch and playing as the character Logan, the glitch will not duplicate the weapon you throw if the weapon is returned to you by Logan's "Boomerang" ability. The easiest way around this is to wait until the weapon you throw to perform the glitch hits the ground. If timed correctly, you should be able to tell whether or not the word "Boomerang" appears on your screen when your chosen weapon hits the ground, and still be able to drop it so that it duplicates itself.
