For study purposes, i.e. working through a topic, I've been using a pear shape. So, this was my first, a simple pear, to work through creating simple patterns. I have to have checks and swirls so those were created first. (Click on any image to enlarge it.)
However, the new Illustrator CS6 has a really fun pattern maker, and using that lets you do even more exciting things. Below is an example.
Two patterns created from the above look like this.