The tutorial that I found the most useful to understanding Illustrator was the Pen Tutorial. It really showed me that the pen tool is incredibly effective and versatile. The Pen Tutorial taught me how to change the size of my stroke to create a different patterns. It also showed me the effectiveness of color and opacity. I will probably use the pen tool a lot to do stretch art, to create game assets, and for coloring and retexturing. I really like the pen selection feature.
This is the image I worked on for the Beetle Car Tutorial. I edited the beetle pretty well. I was able to change the color and it looks good. I didn't really choose the background very well. I should have found a color that supported the color of the car and the logo better.