Quite a few OSes... let's see. lol
Work: Server 2003 (I know! lol), 2008 R2, 2012, 2012 R2, CentOS, RHEL, Windows 7, 8.1 and 10.
Home: Windows 7 (legacy laptop I use for diagnostics), Windows 10 (PC, laptop and Surface 3), openSUSE (Primary boot OS on PC), CentOS (File servers and multiple web servers).
Phones: iOS 9.2 and Android 5.1.1
Other projects not relating to work or home use expand that list further, but to make this simpler let's just say most Windows versions and quite a few more Linux distros. You can add Unix and BSD to that list as well. About the only major OS I no longer regularly use is OS X. Maybe that'll change when I finally decide on what to replace my tired old PC with - who knows. Would be nice if I could find the time to think about that first!
I must have the oldest PC for an IT enthusiast these days. It runs for weeks at a time and I honestly can't explain how more components haven't failed. Getting very long in the tooth now but the SSD drive makes it bearable. Going to be a sad day when it finally bites the dust. lol.
I originally had plans to replace my current computer with a workstation. These days I'm more drawn to my Surface 3 as between that and my Dell Venue work tablet I've got all my bases covered really. So I've been putting some semi-serious consideration into just getting a Surface 4 Pro or MBP 13", docking them when I'm in the home office and buying a Drobo (filled with 4,5, or 6 TB disks) for local file storage.