A Rhyperior planned for the future:
Ability: Solid Rock
Attacks: Earthquake, Stone Edge, Poison Jab, Avalanche
Which nature, set of EVs and item would you recommend?
Adamant Nature +Attack / -Sp. Attack
Careful Nature +Sp. def / - Sp. Attack
Leftlovers - Because rypherior has lots of hp
Focus Sash - To Prevent OHKO from Special Sweepers
Expert Belt - Due to his good coverage moveset
Also, you should replace poison jab for Megahorn, it will give you more type coverage.