This is the distilled information from these two excellent blog posts:

• Finding and purging big files from git history and
• Remove large files in git

First list all the files with the repository with

git rev-list --objects --all | sort -k 2 > allfiles.txt

or if you would like to list unique files

git rev-list --objects --all | sort -k 2 | cut -f 2 -d\  | uniq

Found a file/directory you would like to completely wipe from the repository?

Execute

git filter-branch --index-filter 'git rm -rf --cached --ignore-unmatch directory/' -- --all

but be careful, this might eat your beloved cat!