Question

Most waves are generated by what?

Answer 1

Depends on the type of wave.

Explanation:

Sound waves: vibrations of objects in an atmosphere.
Water waves: Effects of wind, or tidal effects on the surface of a body of water.
Electromagnetic waves (including light) : oscillations in the energy state of subatomic particles (usually electrons).
Gravity waves: Vibrations or collisions between objects having mass

...what did I miss?

Oh, yes. How could I:

Stadium waves: Initiated and sustained by sports fans after consuming one or more overpriced stadium beers.