This is one I use a lot - so much that I sometimes assume everyone knows it.
Using !$ from the shell will expand to the last argument from the previous command.
So, let's say you are looking at a document
$ cat some/really/long/path/to/readme.md
and then you say to yourself, 'self, I need to edit this file.' Bang Cash to the rescue. Just do:
$ vim !$ # expands to vim some/really/long/path/to/readme.md
Or say you are editing a file
$ vim some/really/long/path/to/index.html
and now you want to see it in the browser
$ open !$
Bang! Cash! You are so money and you don't even know it.