I have always really enjoyed the monster designs from the original Star Wars series. There's something about all of the bulky latex costumes that entertains me to no end. They look like they would make the funnest Halloween costumes! I've recently discovered that they are really fun to draw as well.
This one is Ephant Mon. If you look REALLY close in the background of Jabba's palace in Return of the Jedi you can see him lurking in the shadows.