PoziDriv, I've never used. They're the ones like Philips but with an extra four wings aren't they?
I haven't come across them too often, but I've seen poorly made Robertson screws before. They're either slightly too big, slightly too small or they're just not square to the bit. A complete pain in the ass. The two times I came across them I knew by the third screw they were garbage. It was cheaper just to throw the box out than waste the time taking them back.