I find time accuracy to be ridiculously interesting, and I have had to talk myself out of buying those a used atomic clock to play with [1]. I think precision time is very cool, and a small part of me wants to create the most overly engineered wall-clock using a Raspberry Pi or something to have sub-microsecond level accuracy.

Sadly, they're generally just a bit too expensive for me to justify it as a toy.

I don't work in trading (though not for lack of trying on my end), so most of the stuff I work on has been a lot more about "logical clocks", which are cool in their own right, but I have always wondered how much more efficient we could be if we had nanosecond-level precision to guarantee that locks are almost always uncontested.

[1] I'm not talking about those clocks that radio to Colorado or Greenwich, I mean the relatively small ones that you can buy that run locally.