Man... 3rd gen is so forgotten!
Moonblast/Psychic- Moonblast outweighs Psychic in terms of coverage since the only bonus to it is Poison and STAB but I'm sure you have something on your team with Earthquake, right? Not only that, Moonblast covers a lot more threats like Dark and Dragon. And since 6th gen lowered the power of a lot of popular moves INCLUDING Psychic, Moonblast is preferred.
Shadow Ball- Useful coverage since 6th gen brought back some old friends like a specific yellow spoon master who now has a beard(Alakazam) and amplified a certain evil shadow Pokemon(Gengar). So... yeah! Shadow Ball is really useful.
Charge Beam- Not only is the boost to special attack useful, but the coverage against water and flying types like Greninja and Talonflame make it really worth it. And Grass Knot isn't the best since no boost, too many heavy Pokemon resist it, and it is just not reliable on Lunatone.
Rock Polish/Calm Mind/filler- Use it when you can for max sweeping potential. Ice Beam is a bit redundant now so use your imagination when replacing Rock Polish/Calm Mind.
Lunatone has no special Rock attack just like Solrock has no physical Psychic attack is a useful fact when doing movesets for this guy. Lunatone can pull off a Modest, Timid, and Calm nature so it is a matter of taste. 252 HP/128 SAtk/128 Spe for EVs.