Probably Buff Orpingtons, mine were always well behaved, and our wyandottes were always submissive. On the other hand, my EEs and Ameraucanas have always been top dogs.
But, dont assume that your banties will be the bottom of the pecking order, it really depends on their breed. I have a banty araucana hen who is always top dog in the pen, and I had a banty roo who kicked the butt of a giant maran rooster that was 3 times his size. I found the maran with his head in the corner and the banty standing on top of him just ripping his feathers out. However, my silkies are always low in the hierarchy because they cant see anything due to their big poofs. LOL.
chel