I just got a Xtorm Powerbank Extreme 9000 for Christmas. I haven’t had the chance to try it yet, but it is IP66 rated, and supposed to hold 9000 mAh – enough for a tablet or 4-5 charges on a cell phone.
I was debating whether to get the Dark Energy Poseidon or the Ravpower 10050. Both have similar storage capabilities and similar IP ratings, Ravpower (IP66) Poseidon (IP68). It came down to cost. The Ravpower cost less than a 1/3 of the Poseidon. Looking forward to getting it delivered in a couple days.