Some people may want to opt for simple solutions for portably powering their raspberry pi. However, not all power banks provide enough voltage to reliably power a raspberry pi. I know on my Pi I had to try a few power banks before I stopped seeing the low voltage warning on my TFT screen.
Those of you who have found power banks for plug-and-play power solutions, please share what you've found works for you. I also recommend listing a brief rundown of what Pi you are using, and what kinds of peripherals your are using that draw power.