My favorite is actually
gentoo, but since it wasn't there, I chose
slak.
BSD is a different story. Linus ( the guy who made linux ) actually wanted it to come out being closer to mimix, but it actually came out looking pretty much a whole lot more like unix. BSD was based directly on unix.
BSD has 4 main distros which kinda small to linux's 100000 distros.
FreeBSD: most common of them, it was developed to be stable and has broke many records like the most bandwdith coming in and out of a machine at once. ( i think it was 2 TB )
OpenBSD: developed to be super secure. They haven't had a security hole in the default install in the past 8 years. (linux can't touch that

)
NetBSD: it can work on anything with a processor. linux has the same capabilites too. They can run on puters, coffee machines, PS2's, PSP's, XBOX, dreamcast etc.
MAC OS X: need i say more?