I assume you want a moveset, not just all the possible moves it can learn in Gen 3. I have a couple of good ones!
Rhydon (M) @ Choice Band
Trait: Rock Head
EVs: 252 HP / 252 Atk / 4 Spd
Adamant Nature (+Atk, -SAtk)
- Earthquake
- Hidden Power [Rock]
- Megahorn
- Double-Edge
This guy packs a punch right from the start, with a Choice Band giving him a free +1 boost with no setup. Earthquake and Hidden Power Rock are STAB. Megahorn is coverage against Grass types, and is also your strongest hit against Claydol. Double Edge is mainly filler, but it's pretty good for when you don't want to predict/can't afford to miss, as it has good neutral coverage and no recoil with Rhydon's ability, Rock Head.
Rhydon (F) @ Leftovers
Trait: Rock Head
EVs: 252 HP / 252 Atk / 4 Spd
Adamant Nature (+Atk, -SAtk)
- Swords Dance/Curse
- Earthquake
- Hidden Power [Rock]
- Megahorn/Substitute
Moves are pretty much the same on this guy, but you have a boosting move too. This lets you hit extremely hard, while still being able to switch moves, and if you come in on a physical attacker, you can usually get a few boosts in. You can also put Substitute in the last slot, as a shield against the pokemon your opponent brings in to hit you.
