sheared screws

[FlytheCoop]

You can use a small drill bit and drill numerous holes around the screw until you can get it loose, push the drill to elongate the holes until they connect with the other holes and eventually you work the screw loose. Fill the holes with epoxy and move on.

[gw204]

Use a dremel with a thin cut-off wheel to slice a groove in the end of the exposed part of the screw. Once you have the groove cut, use a flathead screwdriver to back it out.