Here are some common units of speed:

* Meters per second (m/s): This is the standard unit of speed in the International System of Units (SI).

* Kilometers per hour (km/h): This is a common unit of speed for vehicles.

* Miles per hour (mph): This is the common unit of speed in the United States.

* Feet per second (ft/s): This is sometimes used in engineering and physics.

* Knots (kt): This is used for speed of ships and aircraft.

Ultimately, the best unit of speed to use depends on the context and the specific application.