Has Professor Snape ever given points to Gryffindor? I couldn't find anything like this in books.
As you can see from this handy chart on the HP Wiki (and this rather more detailed list on the HP Lexicon) Professor Snape not only failed to award a Gryffindor a single point, he failed to award anyone a single point.
Pottermore has a nice infographic showing the breakdown of point distribution in the novels. As you can see, the flow of votes only runs one way where Prof. Snape is concerned.