Two is always better than one, like the pair of counter rotating cutting blades on this handheld circular saw that let it effortlessly slice through wood, plastics and metals in either direction, without any kickback. Clearly Hall and Oates, Batman and Robin, and Sonny and Cher were on to something.
The Chicago Electric Double Cut Saw uses a single 7.5 amp electric motor to spin a set of 5 inch cutting blades, in opposite directions, to speeds of up to 4200 RPM. The obvious benefit to having twice the number of blades is also having twice the cutting power, making it easier to hold while sawing through a variety of materials. But the dual system also stops the blades from catching and kicking back, which can be dangerous for the operator.
It also allows the $80 Double Cut Saw to cut in both directions, so it can be pushed or pulled as needed, freeing the user from having to reposition themselves. It's a clever idea, but far from original. I've been slicing bread with two knives and shaving with two razors for years now. I just never got around to patenting it. [Harbor Freight Tools via Red Ferret]