I LOVE THE WALL-BOMB! One could kill if swung in the right or wrong direction, or fell from a ledder.
My gizmo for fishing, and works great too, is a small VERY powerfull rare earth magnet on a string. Drop it down a wood framed wall with your linemans stuck in a hole at the bottom and pull it out. For insulated, or steel stud walls, I thread the string through the eye on the end of the fish-stick, (like a fishing rod...) get it near the linemans and let the string go loose. Find a ball of insulation stuck to linemans, and magnet with string inside. (Also works if you drop linemans or other stuff in the wall!)
