The Craftsman Hand Impact Driver has helped me on numerous occasions to remove stuck screws and bolts. You just combine the 1/2″ driver with an impact socket or included screwdriver bit, then hit the end of the driver with a hammer to break lose the fastener. I used mine for removing motorcycle case and tailgate fasteners.
The hand impact driver needs no air or electricity to operate, just a hammer. It’s great at removing automotive and motorcycle fasteners that have a Phillips head, but there is a learning curve because you have to twist the head of the tool in the direction that you want it to turn.
Street pricing is about $23 for a set that includes #2, #3, and #4 Phillips and slotted bits.