First? Redhat.

Used? Gentoo, Debian, Mepis, sidux, peppermint, mint, fedora, cachyos, puppy, damnsmall, evil entity, suse, opensuse, Slackware, arch, and who knows how many more.

Using right now: Debian, fedora, cachyos, opensuse, Slackware. Different distro depending on need and device.

Favorite? Real soft spot for mepis, it made it easy back in the day. Fedora right now: it always just works, there is nothing to do just update and move on. Also Debian. Because Debian.

Worst: Ubuntu. Such a piece of crap, always breaking since first release.