One of the most unsung, but most useful, things to add to your suitcase is a package of RediTape Duct Tape. It’s the regular duct tape you know and love, but comes in a reasonable length “flat pack” that makes it easy to pack. (You can get it in multiple colors, too. I prefer white, which looks less industrial than the typical silver tape.)
What will you use it for? You’ll surprise yourself at how many uses you discover. The adage that “when all you have is a hammer, everything looks like a nail,” becomes true — a good, strong piece of tape solves numerous problems: inside pants that need hemming or repair, suitcase and shoe repairs, first aid, automobile cabin rattles, tamper-evident bag seals, and hotel room peephole privacy covers. (Yes, it’s paranoid, but sadly actually happens.) I’m confident you’ll find even more ways to use it once you have it on hand.