Git GUI client for Mac OS X

Since I switched to primarily using a Mac a couple of years ago, I've been on the occasional lookout for a GUI client for Git without much success.

Late last year Tower launched in beta and is looking quite promising. I haven't had much chance to play with it yet, but have been impressed with what I've seen so far.

Aside from Tower, I've found the built-in Git interface to Jetbrains' awesome Ruby IDE, RubyMine, to be really nice as it's built in as part of  the development workflow. It's far less visual, but probably more useful as you work on stuff (assuming that's Ruby!).

Related: Git GUI client for Windows.