I'm a casual battler. My goal is to just raise a nice variety of Pokemon, so I can have a variety of teams to play with. Some members will remain largely static, floating from team to team (Runaway is one of those, with Mewtwo around for cleanup, though he's slated to be booted off soon), while the lineup changes as I raise new members. I plan to start raising some Water types, once my current lineup is leveled, and I may boot Mewtwo off the team just to make room for a new benchwarmer.
So, if anyone does catch me online and want to battle, my current lineup does have Mewtwo on it. His moveset is weird. He's there for crowd control and general cleanup duties while benchwarmers level. I also have a few slaves. It's not a competitive team; it's a utilitarian team. Hence why half the team are slaves.