Been into computer hardware for not very long and got dragged into the Small Form Factor PC space immediately.
The pinnacle for me for a while what getting recent hardware into a PC case as small as a shoebox
I've started with PCs as small as 20L and now have my PC in a case less that 10L. The urge to go smaller while maintaining the same amount of power is hard to resist.
There are others doing full custom watercooling loops in PCs smaller than mine but that is a whole other rabbit hole i don't think i am ready for.
For simracing - a set of pedals with a load cell brake. Building muscle memory for the force you push on the brake is so much better than trying to be consistent with the angle of your ankle. The consistency you can achieve with braking is unreal.
Home espresso - a set of accurate scales and a timer. Reducing variables when trying to dial in a new bag of beans or when chasing that perfect cup is so handy. Like the the load cell brakes for sim racing, it allows you to be consistent and just change small things at a time and then stick to what works.