In my latest run, my team consists of Charizard, Greninja, Whimsicott, Metagross, Chansey, and Dusknoir.
Charizard performs quite beautifully; every time I send it out, it always manages to take down at least two of opponent's Pokémon prior to being taken down. If it's in-game, then even better; it could defeat foe's entire team. Same goes for Metagross. Greninja's pretty easy to utilize, too. It's taken me a while to get used to this Pokémon, considering how new it is to me and whatnot (generally, it's new to a lot of people).
Chansey makes a great staller, and is able to withstand dozens of special hits. Dusknoir is similar, but it could endure both physical and special (oftentimes, though, it's former). As for Whimsicott, I have it mostly due to its Prankster ability, which makes it pretty fun to battle with!