Packing lists are easy to find all over the internet.  But let's take a look at The Professor's essentials of packing list:

Apple iTag:  Just slip one of these into your luggage, handbag, or even into your wallet and you will always know where everything is by tracking the exact location on your phone.  For such a low cost it brings lots and lots of peace of mind. 

Power Converter:  Outside of the U.S., you are going to need a way to charge devices.  This is the best one you can buy.  

Scissors:  What do I need scissors for?  Once you bring them, you will never again travel without them.  Cut off those tags airlines put on your bags.  Trim threads from clothes.  Child safety scissors do the job and they easily go through security at the airport. 

Eddie Bauer Rainier Pants:  We started wearing these about 5 years ago pack them all the time.  They are comfortable, light, look good, and dry fast.  The best pants you can wear for travel. 

Travel Carbon Monoxide Detector:  Probably not needed in a good quality hotel, but what if you are in an AirBnB and you just want to be sure.  This can save lives. 

Suitcase Lock:  I know you thought about this before, but this is one The Professor recommends.  TSA approved.  

Portable Travel Door Lock:  Incredibly light and easy to use.  Incredibly effective in keeping people out of your room.