Having first appeared in the original Pokémon games Red & Blue, and appeared in virtually every mainline Pokemon game since, Rhydon is one of the most frequently recurring species of Pokemon. Furthermore, according to the series art director/character designer, Ken Sugimori, it was the first Pokémon to be designed.
A dual Rock/Ground physical powerhouse that resembles a bipedal rhino, Rhydon has high HP, Defense and the (tied) highest physical Attack stat of any Pokemon until the 3rd generation of Pokemon games, at which point its strength still remained exceptionally high. It has also always been able to learn a wide variety of moves through Technical Machines and breeding, like Thunderbolt, Fire Blast, Surf, etc.
Rhydon is not a well-rounded Pokemon however. It suffers from low speed, and its low special stats means than many of the abilities it can learn are of little use to it. Additionally, as both of its types are weak to water and grass it takes massive damage from attacks of those types, and is vulnerable to single hit KOs from any reasonable powerful attack of that type.