Commandline with the occasional usage of [tig]( https://github.com/jonas/tig ) Once every few weeks I'll use [Tower]( http://www.git-tower.com/ ) for quickly looking up old commits
+1 for tig, which is an awesome tool. I tend towards it mostly for walking through commit history, but it also works very nicely for staging files selectively (and is very good for selecting individual hunks in a larger changeset).