Once you acquire the SC-20, you can fire sticky cameras. What you may not know is that you can fire them at the heads of enemies and knock them out without using your other weapons.

You can also pick up the sticky camera after you fire it (provided you can get to it) so you technically have an "infinite" number of chances to stun guards and other people.

If your camera is fire into a spot that you can't get to, you can try firing on it to "bounce" it somewhere where you can retrieve it.