Usually, my teams have various types of Pokémon. Of all these team, I would say my best one would be consisting of Togekiss, Gyarados, Dusknoir, Breloom, Cresselia, and Brongzong. It was pretty well-balanced; Bronzong, Cresselia, and Dusknoir were playing as walls, and Gyarados, Breloom, and Togekiss were more for the offensive side of things. When put together as a group, they were able to go up against more or less anybody.
As far as mono-type teams go, thus far, I've tried only about two. Can't remember what my first one was, but as for second, it was fire, which carried Ninetales, Heatran, Chandelure, Charizard, Rotom-Heat, and Emboar. It wasn't so bad, really; if you ask me, it was actually pretty fun to utilize.
At some point in future, I'd like to give dragon-type team a go. I'm not exactly sure what Pokémon I'll be having in it as of yet, exactly, but if I had to guess, one would probably have to be Salamence.