If you band a Benalish Hero (1/1, banding), a Mesa Pegasus (1/1, banding, flying) and a War Mammoth (3/3, trample), they can collectively do 5 damage. Two of the three creatures have a special ability other than banding: flying or trample. These abilities still apply only to the creatures that possess them. Therefore, the Pegasus still flies and the Mammoth still tramples, but the others don't.