Lasers come in many sizes and shapes and operate according to a variety of physical principles. Many actual lasers and laser-like systems even occur in nature. Basic laser concepts will be reviewed, and several unusual lasers will be considered. Laser-like acoustic and electrical feedback oscillators invented more than a century ago will be demonstrated. The periodic feedback oscillations that were discovered 200 years ago in falling water sheets (waterfall lasers) will be illustrated using video recordings of several of these striking systems.