Today I learnt about --ignore-rev with git-blame. Super handy if git thinks moving some code made you the author.
$ git blame --ignore-rev abcdef source_file
(Turned out I was still the author, but several years earlier!)
Neat Emacs package of the day: git-messenger: https://github.com/syohex/emacs-git-messenger
It's a popup for git blame on the current line. Feels much lighter weight than displaying blame information on the whole file.
Rather than opting-in to git blame, it would be nice if IDEs showed metadata on the current function by default.
It'd be really valuable to know "this function is frequently modified" or "this function has had N distinct authors". It would help your intuitions about the code.