You are going to get as many answers as there are pedal systems on the market. I use plain old standard SPD's, sometimes (erroneously) called "mountain SPD's" by people. They can be fairly inexpensive and are available in a wide range of types to suit different needs. My utility bike has pedals with SPD on one side and platform on the other. The road bike has a 1 sided road style SPD. The tandem has pedals with SPD clips on both sides so I can get clipped in quickly whichever side is facing up. I like the choice and compatibility between all my shoes and bikes.

The speedplays are pricier but do sound appealing.