I use something like this but I initialize the file with the contents of the clipboard. I use xclip but I think xsel can do the same. Here's a snippet:

    xclip -o > "$tmpfile"    # initialize file with clipboard contents
    gvim --nofork "$tmpfile"
    xclip -i "$tmpfile"      # push file to clipboard

Bind it to a global hotkey and you can use it from anywhere.