Grand Geyser goes off every 12 hours, +/- 2 hours, and can hit almost 200 feet in height. It was worth the almost 3 hour wait!
Daisy Geyser, in the Upper Geyser Basin, can shoot more than 75 feet high, and erupts approximately every 3-4 hours.
Old Faithful eruption back lit. The steam rises 150+ feet.