To be a modern "renaissance" scientist, in my view it is not sufficient just to be a broad polymath. There should also be an element of the eccentric, better still pseudo-scientific, on top of good scientific work. For this my model is Newton, who managed on top of all his ground-breaking scientific work to take an interest in alchemy and religious theory, for example dating the biblical creation.

A couple of genuine polymaths, with an element of the slightly mad thrown in:

http://en.wikipedia.org/wiki/Fred_Hoyle
http://en.wikipedia.org/wiki/Thomas_Gold