For me it’s PeppermintOS.
I started my Linux adventure a few years ago, and haven’t owned a Windows PC since.
I currently use Arch on my main rig, and I wanted to install Linux on two old laptops that I found laying around in my house
I then remembered the first distro I ever used, which is PeppermintOS, and I was amazed at the latest updates they released.
They even have a mini ISO now to do a net-install with no bloat, with a Debian or Devuan base.
Sadly, I believe the founder passed away a few years ago, which is why I was really happy to see the continuation of this amazing project.
I can’t say how popular it is amongst Linux users/fans, but Sparky is pretty cool. I had it on my shitty laptop for a while because I need a distro that worked with low ram and storage.
Also, not Linux based, but I’d love to see more work done on the Amiga based AROS. It’s hella niche, but I’d work on it if I had the knowhow and skills.