this is best, but not exactly necessary. I've removed several bindings with just a #3 screwdriver, and even did it once with #2, but it was extremely sketchy so I wouldn't recommend it at all. If you have a #3 phillips head lying around you can use that, if not, just spring for the pozidrive #3 it will help a lot. If you end up using just the #3 just be careful, take you time, and keep the screw as straight as possible when unscrewing it.
Also, some bindings have "hidden" screws, Griffons being one of them, the toe piece has 3 screws even though you can only see two. Simply unscrew the two you can see, then DON'T try and pull the toe piece off the skis, it's still attached, instead, pull it down towards the heel piece and it'll come off, but you'll notice the black part stay attached, which will show you the third screw.
~WAKIN' UP THE NEIGHBORHOOD TONIGHT!~