Void Linux for the arch and gentoo crowd. It's a system that can be assembled more cohesively.
Nix and Guix - the ideas they bring to the table are revolutionary. I prefer Guix due to its use of Scheme (guile). But Nix is more mature and has more packages.
I've used Debian for years but tried Void on a really low spec netbook and it's pretty nice. The install is pretty painless and not having systemd is an interesting change for me.