I use !!:$ occasionally.

If I wanted to do the cat/vim switcheroo you described, I'd more likely do:

  <UpArrow><Esc>vcwvi<Esc>:wq<Enter><Enter>

Which is a greater number of keypresses, but more flexible and requires less thought.

...as they say: Unix is user-friendly — it's just choosy about who its friends are.