Slackware was my very first Linux (Slackware 3.6). Back then I built a Linux From Scratch (2001/2002) and used it for two semesters and it really helped me fully understand a lot about Linux.

Today I use Gentoo on my main box, Alpine on my file server (I wrote this on using Alpine with full disk encryption: https://battlepenguin.com/tech/alpine-linux-with-full-disk-e...), Void on my router and Dedicated server.

My favorite current distros are currently Void, Gentoo and Alpine.