One thing a haven’t really used until recently is MMS. However, I’ve recently being fiddling with it quite a bit. Not only can you take pictures, record sounds, add backgrounds and send them, but you can also use animated GIFs. This is pretty useful if you want to say, “Hey, you’re late!” or something. You could use this…
All this is now explained in a “how to” here with example GIFs available for download here (need to login).