The PMI Maxx55, a basic plastic blowback designed to shoot a smaller, lighter hitting paintball (sound familiar). Used a proprietary .55 cal ball.
Before the .68 cal Reballs there was the .68 cal Lazerballs, which were softer and more Nerf like but didn't shoot the same as a normal ball so they weren't as good for practicing. But before even that there was the .80 cal Lazerballs. The first fields to sign up for the concept of a reusable paintball didn't want something players would want to steal for use in their guns at home, or have players sneak regular balls onto the field and make a mess, so Lazerball teamed up with Brasseagle to make a .80 caliber Stingray. The concept didn't last long. (But I still managed to find a pair of the guns and a thousand balls for my collection