One of my favorite tricks to use in animation is the wipe. If you need a quick action and don't have many inbetweens to work with, a wipe is always a good way to go. I used to do an exercise where I would watch cartoons frame by frame on the old VCR, just to see how they did the wipes. One of my favorite shows for good wipes was Tiny Toons, they were pretty extreme with some of their wipes. Here's a wipe I used on a project I am working on.