A keyhole saw or drywall saw works best for cutting drywall. These saws have a drywall-specific blade that is pointed, narrow, and equipped with sharp teeth. They can easily maneuver in small spaces and make precise cuts thanks to their long, flexible blades.  For wider cuts and straight lines, you can also get good results with a fine-toothed blade on a circular saw or an oscillating multi-tool with a drywall cutting attachment.