This one item puts three outlets and two USB ports in your bag. Pack it!
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. On a trip to Stockholm, years ago, I threw this SurgePlus USB swivel charger ($35) into my bag at the last minute, 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. I still use it on every trip and it was an incredible investment.