Are many exoplanets synchronously tidally locked like Mercury?
GJ 581d and GJ 667c are candidates for showing spin-orbit resonance.
This paper mentions GJ 3634b and 55 Cnc b as two further candidates.

Spin-orbit resonances different from 1:1 are expected to be rather common among rocky planets orbiting close to a star. Direct observational evidence is difficult to obtain; results are based on model calculations.