Most of us are familiar with the M2 “Pin and Pineapple” Grenade. The problem with the Pineapple Grenade is that it is so oddly shaped that it was difficult to throw accurately. It had characteristic grid patterned grooves to aid it in fragmenting and to help hold it.
The problem though is that its oblong shape tended to make it wobble when thrown and because it was oddly shaped throwing it accurately was a problem. So the T-13 “Beano” grenade was developed to replace it. Most every American boy knew how to throw a baseball. That said, the T-13 was shaped exactly like a baseball and was only slightly heavier. While The US eventually created a fragmentation grenade that looked like a round ball, the T-13 was the first.
During the invasion of Normandy, several of these grenades exploded prematurely and they were all recalled. Surviving T-13s are quite a collectors item.