I can’t really see a practical use for this tip, but I love it and I don’t want to forget it, so I am placing here.
set rl! <– Reverses all lines right to left.
g/^/m0 <– Flip the file upside down.
The latter of the two could come in handy if you have a list that you want inverted. The first would make a good prank for on a fellow admin (put it in his or her .vimrc file. :)
Once I had to flip a file upside down, and I did it with: :%!tac
It is nice to learn a simple pure-vim solution