This one item puts three outlets and two USB ports in your bag. Pack it!
I just spent a wonderful week in Stockholm. I went for #WindowsonLocation and stayed a couple of extra nights to tour the city. I never check a bag since a lost-baggage debacle a few years ago turned a trip from simply hectic to total, frumpy madness. So I carefully consider every item I put into my carry-on bag. At the last packing minute, I threw this SurgePlus USB swivel charger ($15) in, thinking, I’ll only have to bring one adapter.
It was genius. One power adapter got me two gadget chargers and three outlets. I used it constantly to safely charge my tablets, phone, and laptop. It also made my curling iron possible. It’s going in my always-bring-on-a-trip bag.
[Update on January 30, 2019: I still bring this with me on trips. It was a great investment.]