Use ThunderPunch since it covers from Water Types..
Also Fire Punch covers from Grass / Ice Types.
I'm using this Rhyperior in my team -
>Rhyperior @Expert Belt
(Shiny Rhyperior) Adamant Nature
EV's - 252 HP / 252 Attack / 4 Defense
- Stone Edge - Stab and high chance of Critical-Hit, don't go for Rock Wrecker..
- Earthquake - Stab.
- Mega Horn - Have great power, not to talk about the Rhyperior's Attack stats...
- Thunder Punch / Fire Punch- This is your choice, I'm using Thunder Punch. -> Thunder Punch covers from Water and can paralyze. (10% of paralyze). Fire Punch covers from Grass /Ice and Steel and can burn. (10% of burn).
Also Expert Belt raises super-effective moves by 20% + Rhyperior's Attack!