Well, Thunder will do a lot of damage to Steels, Dialga will resist flamethrower and Thunder due to Dragon typing. I currently run Shadow Ball, Aura Sphere, Ice Beam, and Protect. Shadow Ball for Giratina, Mewtwo, Latios, and to hit Kyogre for some Damage. Just thought of something, having Ice Beam does nothing for me, I will be switching this to Grass Knot.... Um...Aura Sphere is for Dialga, T-Tar, Normal, Dark, Rock, and Ice Pokémon. And Protect for protection. Now that I think about it, Ice Beam (and other ice moves) are useless moves on Mewtwo, I don't see what it can KO that isn't covered by other moves, if you can think of one....