Anker 2nd Gen Astro3 12800mAh External Battery..
Why? It was the first Anker product I purchased (Dec '13)... I got it because we were planning another trip to Disney World and I needed to keep my phone charged while in the parks. I like that it has 3 ports, is relatively small, but charges my phones, my ipad, and my Nikon S8200 camera I has never let me down and continues to work. Even though I now have newer Anker portable chargers, I still keep this in my bag.
Oh, and since my first one worked so well, we even got one for my wife in July '14, for her to use on our other trips, and now while she travels for work. She uses it for her iPhone and iPad. Its still working great too, and gets used all the time.