On Pearl, I beat E4 with Empoleon, Torterra, Luxray, Staraptor, Rapidash, and Whiscash... But after learning how often most of those pokemon are used... For my Diamond game, I plan on using Infernape, Roserade, Girafarig, Gyarados, Chatot (mainly HM slave), and Rampardos. It'll be a few days though, because I haven't yet beat the fourth gym, but those are my plans.