Music, without a doubt. Specifically, being able to choose particular songs to listen to. I'd get pretty miserable after a few days.

Toilet paper.

Housing. (Again)

Literally, depending on where you draw a line between luxury and important but not mandatory for most people, it's air conditioning. We have three people in this household that do very poorly once heat and humidity starts to climb, including myself. Plus, uncontrolled humidity in the south ruins things, so there's an increase in costs associated with whatever decrease in power usage would save. For us, AC is right on the edge of being a necessity, as in a medical thing.

But in a more literal luxury that serves only pleasure or want, chocolate. No nutritional necessity, and it isn't like we all can't do without it. But gods damn, it would hurt. A nice piece of good quality dark chocolate is the ultimate mini reward for me. Do something incredibly painful and time consuming, that bit of chocolate is enough to turn it from something that I'm weeping in pain trying to finish into something I'm able to get through before I break down. That's a luxury, but fuck me if it isn't something I lean on heavily as a crutch. I really don't know what I would use to coax myself through really bad days where I'm barely functional but still have to function.

Caffeine

Soap and clean water

Private space. I used to share one room with my siblings. It was alright as a child, but I don't want to go back. And I know that many families around the world have very little space for two, three or four generations living under a roof.

Indoor plumbing and summer time AC

My headphones. I just love listening to music way too much.

A/C

that picture exactly

Hot water!! I don't remember how I survived childhood

healthcare

Contact lenses. I know I could use my glasses, but I put them down and can't find them half the time. I am blind enough to be absolutely useless in most situations without corrective lenses.

Biggest one would be AC, followed by cheap electricity, and internet. Maybe frequent sex too. To quote that recent Mengzi post 食色性也

Meat, specifically ground beef

I genuinely think I'd go insane if I wasn't able to buy Brie or Blue cheese. I don't need it every day of course, but any less than once every two months would be unspeakable

Cheese in general. Chocolate as well. Clean water is a necessity, but I guess hot water on demand? While I like eating beef and chicken I probably wouldn't be that sad overall if it went away.

Sharpening stones and files. I can't imagine using dull knives. I can't stand knives duller than hair popping sharp. I have excellent knives that hold a crisp edge and I sharpen those every 30 minutes of super fast chopping (10 seconds on a 9k stone).

Not just knives but scissors, trowels, shovels, cooking spatulas, dust pans, vegetable peelers, can openers, toenail clippers, all need to be sharp. Not being able to sharpen all of those would be a tragedy.

If you are delaying getting into sharpening, just do it. It will serve you for the rest of your life, and I sharpen every single day (I'm a woodworker). Its truly a luxury to have sharp tools, all the time. So satisfying.

Aside from that, chocolate. The cravings will never go away.

Air conditioning, but I would argue that is a very expensive necessity.

Electricity

None that would "break me" if I didn't have them, but I spend the vast majority of my free time on my computer (by choice, I have friends and outside activities I can go to if I want), and whenever I've had to be away from it that's always been the toughest part.

Private Space. My own private Bedroom Especially. Also, a good bathroom. Especially a good toilet and shower. Make them clean too.

If there is a luxury whose absence would break you, then I would suggest you do a little "fast" from it, occasionally.

Healthcare, condoms