A screwdriver set with all the tiny weird heads that you almost never would use. I got one as a gift and it's been really useful

I can't think of it

Got ex-lease pc workstation and rebuilt it into a Linux media centre/MAME box

A set of precision screwdrivers.

Goes from like 4 dollars to 40 dollars

No more jamming in a knife and stripping the screw for changing batteries etc.

You can even go all out and get the tamper proof torx ones as well.

Some whole ago I bought an USB rechargeable fan/unduster thing which is surprisingly powerful.

It didn't have a particular need, you can use your lungs to blow air after all, or fall back to physical. The low price got me interested and to buy.

I bought a smart watch for 12 €, which I wouldn't have bought over 15 or 20 because I had no need or particular want.

More than checking time it tracks my pulse, steps, and sleep.

There's this product called grab-a-rag... They are washcloth-sized washable microfiber cloths.

Comes in a large box (think maybe a box that new boots would come in) but it's exactly like a box of tissues - pull one out, the next emerges halfway.

Once I wash them, I don't reformulate this tissue box set up, I just throw them in the drawers, I use them for wipes, I wash the floor with them, I have some set aside for dishes. They are mind-bogglingly good for cleaning surfaces.

I give mitt-fulls away because they're so cheap, and people freak out about how great they are.