Sometimes I need to pull a complete copy of a previous file out of a github (this is useful when needing to do visual binary diffs to see which bytes have moves or changed).
To pull a specific file, say the last commit, the following command line does the trick:
git show HEAD^:./myfile.bin > myfile.bin
HEAD^ means "one commit behind the head of the branch" (the "head" being the last commit on the branch). Though if you've got merge commits where a commit has more than one parent commit this can get a little complicated (which why I tend to stick to just the previous commit).
HEAD^2 means "two commits before the head of the branch". There's also detailed stackoverflow post about the difference between the caret
^ and the tilde
~ with examples of how they traverse up the tree.