You know all about Alexander Graham Bell's telephone. But did you know Bell also made a metal detector in an unsuccessful attempt to find the bullet in President James Garfield after he was shot in 1881? The device (which came along after one developed earlier in France) is one of many lesser-known creations of big-name inventors like Bell, Thomas Edison, Nikola Tesla, and Benjamin Franklin, as Mental Floss reports. A sample from the site's list, which includes a creepy talking doll: