Here's the scenario: I've got a big file filled with all sorts of eclectic rubbish that I want to regex. I fiddle around and come up with a perfect search pattern by using the / command and seeing what it highlights.

Now I want to use that pattern to replace with. So, I start typing :%s/ and I cannot recall what the pattern was. Is there some magical keyboard command that will pull in my last search pattern here? If I'm writing a particularly complex regex, I have even opened up a new MacVim window, typed the regex from the first window into a buffer there, then typed it back into the Vim window when writing the replace pattern. There has got to be a better way of doing so.