So, we've come to suggesting a Bug/Grass type now have we? I would expect that from Will, but you Swampert? WHY? Are you forgetting that there is a really awesome Grass/Normal type called Sawsbuck?
You'll probably want one with the ability Sap Sipper, as 95 base speed is enough for ingame purposes. And Grass types are a fairly common type. Sawsbuck is great ingame because of all the type coverage it has. Jump Kick, Horn Leech, Wild Charge, and Double-Edge/Return. A perfect ingame Pokemon. Although if you need a Grass type early on and this is for ingame Leavanny might work. I'd know best if I had the game.