Slice Up Drywall With a Multitool
There seems to be no end of odd jobs that can be done with an oscillating tool, and here's another one: If you have to remove a section of damaged drywall, cut it out with a multitool equipped with a half-moon blade. The tool will cut almost as fast as you can pull it. And because the oscillations on the blade are so short and the teeth are so fine, the tool creates half the dust of a reciprocating or keyhole saw. Plus, the recess you cut will be much straighter and cleaner, making the patching work much easier.
Cut Around the Window With a Recip Saw
Spray foam insulation does an excellent job of insulating around a window—and a surprisingly good job of keeping the window or door in place. Even if you remove all the fasteners holding in a window, you won't be able to pull the window out until you deal with the spray foam.
So don't bother pulling the nails or screws out of an old window. Just run a recip saw between the window and the framing and cut the fasteners and the foam at the same time. You may want a buddy on the other side of the window to keep it from falling out when you're done cutting around it. With a long enough blade, you can even slice through the nailing flange at the same time. That's important if you're trying to save the siding around the opening.