The BFG is a simpler, faster alternative to git-filter-branch for cleansing bad data out of your Git repository history:

Removing Crazy Big Files
Removing Passwords, Credentials & other Private data
The git-filter-branch command is enormously powerful and can do things that the BFG can't - but the BFG is much better for the tasks above, because:

Faster : 10 - 720x faster
Simpler : The BFG isn't particularily clever, but is focused on making the above tasks easy
Beautiful : If you need to, you can use the beautiful Scala language to customise the BFG. Which has got to be better than Bash scripting at least some of the time.