What globally unique, persistent, resolvable identifiers do you use for datasets?

What globally unique, persistent, resolvable identifiers do you use for datasets? I want to know about either (a) a challenge you’re facing, and what you’ve tried; or (2) a choice you recently made, and how it’s going.

Context: For each question of the FAIR Implementation Profile (FIP) Ontology, I want to collect and discuss folks' choices and challenges on my podcast, Machine-Centric Science.

Please email me at podcast@polyneme.xyz with:

You may also write out your challenge or choice in the email body, in which case I will read it aloud. If you choose a CC0 license, I will by default keep you anonymous unless you give me attribution info.

Extra credit:

If you really want to send me multiple choices and/or challenges, please send them as separate emails. Also, feel free to spread this message far and wide. Thanks!