The Door Saver II hinge pin serves as a doorstop. It has two interlocking cams at the top that engage the hinge leafs. Since the distance between the two cams is adjustable, you can set different opening angles. The device eliminates the rubber bumper, so it works even if there is no casing (such as for a door recessed in an opening). It installs like a standard hinge pin and works with 3 1/2-inch or 4-inch hinges (though the pin protrudes past the bottom of a 3 1/2-inch hinge). It costs $6.
Perfect Products, 877/366-7728, doorsaver.com.