In my office we use MKS Source Integrity which is great from the Change Management & Workflow perspective. We used to use a combination of CVS, VSS & RCS repositories prior to migrating.

At home and when no one is looking I personally use Mercurial. (my vote) I really like the idea of a distributed system rather than a centralized one. It took me a little while to grok why it's better. I'm sure that everyone who uses Git probably went through the same awakening period to get over the paradigm shift.

The bottom line there is that there still can be a centralized repository but by having distributed repositories feeding into it you can improve the quality of the code that ends up in it. If nothing else it solves the age old debate about if you should check in any time you want or only when your code is working. Only working code should go into the main repository - and feel free to keep all the crap you want in your local one.