Current distributions, I like EndeavourOS sway edition and Window Maker Live (wmlive).
Historically, I liked HP-UX and OpenSolaris with Gnome and the Nimbus theme. Linux Mint Darnya was nice. So was OpenSUSE 9.3 I think with Gnome and its custom launcher. Red Hat Enterprise Linux / Scientific Linux 6 was nice looking. We went a couple of years without CentOS so everyone used SL6.