Here's a great Adobe Illustrator tip I wanted to share with you all. It just so happens that if you hold down the “tilde” key on your keyboard, you can get a neat effect using any of Illustrator's drawing tools. Holding down the tilde key, (the little squiggly line above the tab key, left of the number 1 on your keyboard.) while using a drawing tool will cause Illustrator to repeat the shape rapidly as you move your mouse. Examples are below:
For starters, here is a pic of the tilde key:
Here are some quick examples with some different drawing tools:
Also, remember that you can hold shift and/or option/alt at the same time you're holding the tilde key to constrain your shapes if you like.
Rounded Rectangle tool: