It looks like in your sig that you chose Slaking and Seviper? They seem alright.
Groundon
Armaldo
Ludicolo
Metagross
A water type could do great damage here, super effective to two and neutral to the other two. Ground moves would also take out two of them. Hmm. I don't see too many other weaknesses, though don't use anything weak to Ground or Water... try not to get more ice weaknesses either.
Maybe try a Dark or Fighting type? It depends if you're going for favorites or power.