Since someone already mentioned dashcams and cast iron, my vote is: a bidet toilet seat attachment.

Fancy ones can roll $200+ but a super simple one with just a cold water hookup and no electricity will knock you back $50-60. I bought one right as covid was beginning to hit the west coast, and instantly realized I could never - ever - go back.

Huge bonus of the toilet seat style bidets is that, since you aren't actually replacing the toilet, they take like 5 mins to install and can be done in a home, condo, apartment, wherever.

Jumper cables. For like 10-20$ it can save you or someone else a lot of trouble.

Pocket knife/multitool.

The last thing i bougth around 100€ was a portable SSD, its quit useful for backups and saving big files.

Also SSD prices has fallen in the last minths so you can get a 2TB SSD around 100 and an SSD Encloser for 15€ and your good to go.

PS: Pls, always have backup of your stuff. PLS

A dildo.

Electric toothbrush

Underwear. I mean it would be super weird if you didnt own any underwear, right?

A bedbug proof mattress cover. Order it today. Doesn't matter what sort of life you live, anyone can get them and it's a horror show.

A good chef knife

Also makes and excellent chrismas/birthday present

Yubico Security Key, to secure your logins and more!

A plunger. Get it before you need it.

A meat thermometer. Probably the best 20 bucks I ever spent. Completely changed how I cook meat.

If you have any interest in working on things, a ~$30 set of calipers is an awesome tool for figuring out hardware sizes and so much more. You can definitely spend much much more but as a hobbiest I'd recommend against it.

A few spare charging cables to keep plugged in around the house are always great too, I also recommend keeping one in your travel bag so you never need to think about packing one.

A well stocked toolbox. Not just a random assortment of things but a well considered, well stocked toolbox with everything you need to tackle basic home repair.

To all those saying that tools are too expensive, they are not. Everything you need to tackle most home repair scenarios can be had under $100. Will you be turning screws by hand and adjusting wrenches? Yes. Will it be enjoyable work? Probably not, but you absolutely can have a good set of very basic tools for under $100 then add to it over time.

Get a hammer, adjustable wrench, angled pliers, razor utility knife, and 11-in-1 screwdriver. Buy additional tools as needed.

A good pocket knife or multi-tool like a Letherman or Gerber. I always have a pocket knife on me and a multi-tool in my car. Either one gets used pretty much daily.

Knife: https://www.amazon.com/CIVIVI-Praxis-Flipper-Stonewashed-9Cr18MoV/dp/B08PF6NHLJ (there is a mini version of this if you like/need a smaller knife)

Multitool: https://www.amazon.com/Gerber-22-01471-Suspension-Multi-Plier/dp/B07DD69QN3/ref=sr_1_3?crid=L2L8RHSX7WGG&keywords=gerber%2Bsuspension%2Bmultitool&qid=1691155854&s=home-garden&sprefix=gerber%2Bsus%2Cgarden%2C84&sr=1-3&th=1

Ergonomic Mouse/keyboard

Admittedly for $100 you might have to choose one or the other (though I used a $12 ergonomic mouse from Amazon for years until I switched to a trackball, and I loved it) - but if your job is computer based, you really should consider switching to ergonomic equipment.

Your average keyboard and mouse setup is absolute murder on the wrists in the long run - if you spend more than a couple hours at the computer every day without ergonomic equipment and your wrists don't hurt, then it's only a matter of time.

Granted, it's not just about buying a cool new keyboard and mouse - you also need to cut out bad habits like wresting your wrist on the table while typing and so on, but a good KBM will help you build those habits naturall

A decent pocket sized torch. It'll help you out in man situations.

Honestly, I would recommend a good pair of Bluetooth headphones because it is amazing how simply being able to shut out the world can relax a person.

A "Bullet" style Fisher Space Pen.

People need pens more often than you'd think and you can be their hero. They're nigh indestructible in a bag or pocket and the thick ink will write on many things a normal ballpoint pen can't. I've written on ceramic, glass, wet cardboard, and one time (in the 90's) high school cafeteria roast beef.

The only downside is that if you damage the tiny ball in the ballpoint pentip and then don't use the pen again for a while, the sticky ink can ooze out and make a mess inside the lid.

If you have a car: a fast charger for your phone.

It's amazing to me how many use a built-in USB that barely charges the thing.

A basic set of tools. Car jack, tire iron, jumper cables. Rice cooker, crock pot, and air fryer (probably more than 100 collectively, but each one should be less than 100).

a screwdriver set

First Aid kit

Decent digital instant read cooking thermometer. Makes any meat dish on point.

It sounds crazy, but trust me: a corn cob backscratcher.

It’s essentially just a dried piece of corn on a wooden stick. But the texture is perfect, and because it’s rounded, it covers a much larger area than a regular backscratcher and is much more satisfying to use. My wife bought me one for $11 and I swear by it. You simply cannot go back to a regular backscratcher after trying one.

Oh, and they’re indestructible. My in-laws still use one from 1979!

A pot, some dirt, and a tomato full of seeds to plant.

Like the man says:

Only two things money can't buy
That's true love and homegrown tomatoes

After that? Any herbs you like. Basil, parsley, oregano, etc. are all better when you can just pick them right off the plant when you want them.

A decent flashlight.

A streamlight stylus pro is $20, uses 2 AAA batteries, is barely bigger than a pen, and can be an absolute life saver. It produces way more light and throws it way further than your phone's light, and I've been carrying the same one every day for nearly 15 years now with no signs of it failing. I use it nearly daily in my personal and professional life, you will genuinely wonder how you manages without it if you make it a habit of carrying it.

Or go nuts and get yourself a something like a surefire G2. Bigger, heavier, but more durable and incredibly bright.