The foundation of packing for a trip abroad is a great suitcase and a strong system to keep things organized. You don't want your suitcase to explode all over your hotel room!
These items are key to ensuring that you've always got power when you need it, you know where all your things are, and you always have something to entertain you.
You will absolutely regret it if you travel without these. Murphy's law says it WILL rain if you don't bring your umbrella, and it'll be 95 degrees every day if you don't have water.
I personally love having my regular brands with me when I travel, and these items ensure I can easily bring what I need.