Researching a question from a club member, I read in the FAR's:

§**23.207 *Stall warning.
[...]
(b) The stall warning may be furnished either through the inherent
aerodynamic qualities of the airplane or by a device that will give
clearly distinguishable indications under expected conditions of flight.

Every plane I've ever flown has a mechanical stall warning device (some
visual, some aural), but apparantly it's possible to certify a plane
without one. Does anybody know of any real life examples of planes
certified without stall warning devices?