move-text is a simple Emacs package that lets you move a line or region around using M + ↑ and M + ↓. It's not limited to plain text buffers - you can move lines of source code around too.

In practice it looks like this:

Moving text around

I prefer to use Control + Shift with the up and down arrow keys, so my configuration looks like this: 

(use-package move-text
  :bind
  (("C-S-<up>"   . move-text-up)
   ("C-S-<down>" . move-text-down)))

Cutting and pasting a region is usually quicker, but for shuffling a few lines around this method is quick enough.