Personally I would recommend Samurott, Archeops, Darmanitan, Leavanny, Vanilluxe and Haxorus. Samurott has really decent SP.Atk and can beat certain pokemon in the E4's team pretty easily. Archeops has good speed and atk. Darmanitan's Flare Blitz can really save you from dangerous situations, while Leavanny can beat Grimsley and Caitlyn quickly if you teach it good bug moves like X-Scissors. Vanilluxe can take out Caitlyn's Sigilyph which may pose a threat to Leavanny, while Haxorus is built like a tank, so nuff said.