For version control: SVK. See the SVK wiki, pictoral overview and the slide presentation. Written in Perl, built on top of subversion, and allows local mirroring of repositories. (E.g. mirror my subversion repository to a local depot on my laptop, disconnect from network, have full local version control on laptop, and push/merge upstream when I'm back online.) Also supports star merging, baseless merging, and other nifty features.

I'm also very addicted to unixutils for native win32 ports of standard unix tools. Now I can "cd", "mv", "grep", "less", etc. from my win32 command shell without having to use Cygwin (not that there's anything wrong with it, but I just didn't want to go that route).