Is it us or do screws strip a lot more frequently than they used to? To extricate one, the first thing to do is switch tools. If a drill/driver got you into the mess, it probably won't get you out. Instead, grab a screwdriver with a tip that matches the screw type, and a hammer. Gently tap the tip into the head to set it. Using as much downward force as you can muster, slowly back out the screw.