I'm a Unix sysadmin who started out running UniStride, then played a lot with MINIX 1 on an old PC AT clone, until Bill Jolitz published 386bsd, and I set up a 386 box with that. 386bsd became NetBSD, and that's been my preferred working platform ever since.
For play, though, I tend to have more fun with the older systems. I run 2.11BSD on a MicroPDP-11/83, 4.3BSD on a MicroVAX 650, and good old 6th edition UNIX on a MicroPDP-11/23.
Other fun items in the collection include UniStride 2.1 on a Stride 460, MINIX 3.4 on an elderly PC, Helios 1.3 on an Inmos B008 Transputer board in said PC, using MINIX for its file system and Internet access, and some non-Unix stuff, like working AIM-65 and Osborne 1 microcomputers.