I select some polygons, say 10, and for some reason I dont want some of the polygons that have been selected. Either I restart select polygons from start or there sholud be a key-combination that would let me un-select the polygons that I dont need in my selection now.

selected polygons : ---------
un-select some : -- - - -

this might be a slection set that I might like.

Another scenario might be to select the head group and then remove eyes and mouth from the selection set.