Over in a friendly match against a guy named 'lukeplots,' I ran across an interesting Armaldo set:
Trait: Swift Swim
EVs: 252 Atk / 4 Def / 252 Spd
- Stone Edge
- Brick Break
With rain support, Armaldo can be quite a menace to non-scarfed variations of Mewtwo and Darkrai by hitting them with a STAB X-Scissor. A base 125 attack stat also makes him a good revenge killer, especially with CB bolstering his attack even further. In addition, the rock typing Armaldo has can be used to check Extreme Killer Arceus
The move X-Scissor serves as both STAB and a way to revenge kill Mewtwo and Darkrai, Stone Edge also serves as a powerful STAB option even if it misses sometimes, Earthquake is for the grounded Steels and for dealing out damage, and Brick Break is to deal good damage to both normal Arcues and Ferrathorn.