TortoiseSVN - The coolest interface to (Sub)version control
Vault VCS - SourceGear Vault Pro is a version control and bug tracking solution for professional development teams. Vault Standard is for those who only want version control.
VisualSVN - VisualSVN - Subversion plugin for Visual Studio
Microsoft Visual SourceSafe - Microsoft Visual SourceSafe (VSS) is a source control software package oriented towards small...
Slik SVN - SlikSVN is a free subversion client for the command line.
Mercurial SCM - Mercurial is a free, distributed source control management tool.