I've used vi for 20 years now (gosh), and it's only in the last few weeks that I've actually started using it properly. One example is that I wanted to save in fewer keystrokes; like ZZ, but without quitting. I came up with this for my .vimrc:

  :map ZA <Esc>:w<CR>

I find the vim help very intimidating (with every possible feature and then some), but it turns out to be really simple to create your own commands. I also made ctrl-N go to the next file (ctrl-P for the previous file), because I do that a lot.