Rhinoceros Charge◆◆ The rhinoceros Strides twice, then makes a horn Strike. As long as the rhinoceros moved at least 20 feet, the Strike's damage increases to 3d8+6 piercing damage. A Medium or smaller creature struck by this attack must succeed at a DC 21 Reflex save or be automatically Shoved back 5 feet and knocked Prone by the force of the blow.
Trample◆◆◆ Medium or smaller, foot, DC 18 basic Reflex
Source: Pathfinder Monster Core
Running this fight? Add the rhinoceros to the initiative tracker: type its name and the AC, hit points and Perception for initiative fill in, and the book button shows this stat block mid-fight.