I just got a Chimchar from the GTS and I wonder if it will be useful for my team. I have not beaten the elite four yet(Platinum). My team is:
Torterra, Vaporeon, Garchomp, Staraptor, Lucario, Gengar.
Infernape would suite your team well, as you don't have a Fire or Fighting type already. Infernape can come very handy against the Champions Pokemon with great a movepool and base stats to boost his usefulness. I know this is Ingame, but Infernape wouldn't be in OU for no reason!
A good set would be: (Of course hoping that you have enough potions to run this set well)
This nice ingame set needs potions, but will sweep your opponent easily.
I chose Chimchar as my starter when I was playing Platinum, and I have to say that it is a must have on any ingame team.