Git

Git is a lightweight, fast, portable distributed version control system with excellent branching/merging capabilities, flexible support for many different workflows, and very high performance.

It’s been my VCS of choice since mid-2007. (Before that I used SVK, Subversion and CVS.) It is now so far ahead of the competition (in terms of technical merits) and so firmly entrenched among the development community (in terms of popularity), that it seems unlikely that it will be displaced as the dominant version control system for the foreseeable future.

Official site

See also