Morgans wrote:

This has been done with a extremely swept back shape, called "scimitar",
that as it unloads at high speed, the tips twist back to higher angles of
attack. I am unaware if this is currently being produced. The trick is to
select materials and thickness, to get the twist just right, to work as
desired.

Hartzell, very popular with the racing and nonracing Lancairs...

Nice photo of one he
http://www.ramaircraft.com/Whats-New...-Propeller.htm

Thrust comparison he
http://www.beryldshannon.com/Hartzell/chart.htm