Super27

If you carry one of these and use it, you won't be doing much sleeping in hotel beds

In all seriousness, agreed 100% with all the suggestions thus far. I also used to carry a small pack of shoe shine wipes and a pack of Tide wipes (or the Tide to go stick works too). Earplugs are also a must, for both hotels and walk-arounds.

If you're a commuter, invest in good noise-canceling headphones. I also recommend a non-descript black shell jacket or fleece zipper-up. Something you can wear both on overnights in a variety of weather, and over your uniform for commuting. Keeps you a little more incognito in the terminal and on commuting flights/deadheads - take off the tie and throw your badge in your pocket and you look like any other businessman in a white shirt and slacks. Personally I used to wear mine throughout the trip as well, but I guess that would depend if your company is strict on uniform dress code. Amazon has some great inexpensive options in their house brand (Amazon Essentials).