I can see seperating wings and centers (different positions), but why left & right wingers? No one seperates left & right Dmen.
Mike Modano is a natural center who was drafted as a center, but played RW until around 1993 on the relatively center-deep Minnesota North Stars.
Keith Primeau is a natural center who was drafted as a center, but played primarily left wing until Steve Yzerman's neck injury in 1993. He played center much of the remainder of that season, before moving back to the LW. He shifted between the two for the next two seasons before being traded, and spent the rest of his career almost exclusively at center.
If we were to take the period just from 1990 to 1993, Modano is a RW, and Primeau is a LW. And if we want to go further, Pavel Bure is a LW, and Mats Sundin has spent more time on the wing than at center, although he's been shifted across both wings.
If we want to use 1995-96 exclusively, an argument could be made to classify Mario Lemieux as a LW and Sergei Fedorov as a RW as they each played probably about half and half that year, if not more on the wing.
Dany Heatley has already been addressed, of course. He's played quite a bit of both sides.
Sid Abel, Alex Delvecchio, and Mark Messier were all postseason all-stars at both C and LW.