I've used all of: SCCS, RCS, CVS, SVN, and MS VSS for source control/revision control/whatever you call it.
And... I was going to say, all but CVS for work, until I remembered one project I was one which used CVS. So I've used all of those at work, at some point or another.
Oh wait, I should also include Rational wossname... *wikipedia* ah, no, Synergy (now apparently "Telelogic Synergy", though I don't remember that name; ISTR it was "CM/Synergy", or something like that, at the time?). Which was probably the most painful of the lot, and the only one where we had basically a full-time Synergy guru whose job was to un-snarl things when things got snarled, which was more often than I'd have liked, and otherwise provide support. I also had a hard time getting into the mind-frame of knowing beforehand which files you'd be working on so that you could check them out as a bundle and then check them back in again at the end—I preferred being able to pick which files to check in (e.g. some of them earlier since they seemed stable, others a bit later when I was still working on them).
FWIW, I used SCCS and RCS in the same project, on a HP-UX 10.20 machine. (The sources for an older module were managed with SCCS, those for later modules—which were originally from another company, but we took over maintenance for them—with RCS.)