Certbot and acme.sh are the most popular dedicated linux clients (.e.g. software you would install separately just to manage ACME certificates). The most popular clients on Windows are win-acme, Certify The Web and Posh-ACME.
What's best for you will depend largely on your requirements but for instance a user running linux for fun who wants to use Apache or nginx would probably use either Certbot or acme.sh, but if interested in modern web servers when they'd quite possibly choose Caddy instead. Users who are trying to configure kubernetes would probably use cert-manager.
Organisations which are running custom hosting solutions will either integrate a popular library or just build their own ACME client (some orgs prefer not to have external software dependencies).
There was an old PDF somewhere with more detailed user-agent statistics but I can't find it.