What are good items to pack for a deployment?

batteries (AAA, AA, C volt), 100mph tape (alot), 550 cord (alot), zip ties, 2 decks of playing cards, spare charging cords for any electronics you plan on bringing, a spare bed sheet (trust me), extension cord and power strip, and lastly something that holds value to you, whether it be a ball cap or whatever.

Don't bring a PPD. Customs won't let you bring it back. You'll probably get a brief on it, but soldiers don't always listen to briefs.

Power adapters. Most, if not all, electronics nowadays will auto-convert between 110v and 220v. Apple plugs all do as do HP laptops (that's what I had). A plug to adapt to the different standards is useful (i.e. US three prong to Kuwait/Iraq three prong, or two prong Euro). Voltage stepdowns are bulky and heavy so if you bring one just be prepared otherwise try and get one when you get there.

550 cord, 550 cord, more 550 cord. An extra woobie, reading material.

Depends where you go in CENTCOM and what you'll be doing.
Crocs are no joke, 10 years ago and today, get yourself a pair or at least knock offs.
Entertainment of your taste and plenty of it. If you have bad habits (i.e. nicotine) get a reasonable amount, 3 years ago there was a bit of a shortage in the region for a month or 2.
In general you should have... Modest access to pleasantries where you go. If you are able, I recommend, now packing some personable desirables in a mailable box with things like: pillows, sheets and blankets, more sin if you need it, etc. To mail to yourself if per se you end up on a FOB and receive a CHU or barracks style life... If you know you are going to end up in a PB(don't know if they still exist) then ignore that list and pack things like: I can't stress this enough: SOCKSSS.
Generally most places in CENTCOM have a decent mail run nowadays minus 1 country that comes to mind, another is just honestly another duty station. Do without posting where for OPSEC, search around for info to your AO for what to expect.

Depending on your command and location I would pack a shemagh. They've been around for millennia for a reason. As someone else said Crocs are perfect for the hooch. Quality headlamp too.

What do you want to do when you have free time? No matter what your unit will supply you with food and water. CENTCOM has a lot of conveniences. They have the best out of all the units that are in the theater. Otherwise, pack light. CENTCOM is a major command. It has a lot of resources. US government stamped, made by the blinds and the disabilities, ballpoint pen is the only pen that never quit. Others quit working as soon as your boots hit the ground.

A good multi tool/knife, good shower shoes, at least two full size towels, as those army browns are worthless, a seat cushion, because most of the chairs or vehicle seats will be ATFU. A decent pillow. Shoe insoles, not those cheap as Dr. Useless's ones, but something around $20 a pair or so. Put them in each pair of shoes you are taking. A good rifle cleaning kit complete with a bore snake. Spare batteries in AAA and AA. Wool Socks, as they hold up better than standard issue, I like Thorlo's. KY, because in one way shape or fashion you are going to get screwed, so be ready for it. lol