I've been using the a 5,000mAh Anker power bank for a few years now. 5,000mAh is a good balance between physical size and battery capacity, especially if you're just heading out the door for a long day and want a little extra battery life.
But for long flights and trips I wanted more power. This is one of Anker's latest Qi2/MagSafe-compatible power banks featuring faster 15W wireless charging. And it has a fancy, albeit unnecessary, little display that shows not only the charge level but also the time until it's fully charged, or depleted.