What co2 pellet guns shoot rubber balls?

First, Pellet guns don't shoot rubber balls, they just shoot pellets. But I know what you are asking. I believe you are asking about RAM (Real Action Markers) paintball guns. These guns shoot a .43 caliber paintball or Rubber ball, not the much larger .68 caliber paintball that is associated with Paintball games. RAM guns are used for training by the police and other agencies. They feel just like a real firearm and even have blowback when fired.

Umarex co carries a line of RAM guns. See the link below.