Before I came back to school I spend two years designing and prototyping a hanging planter which I was hoping to bring to market. I did significant research into materials and manufacturing options as well as the gardening industry. I wrote a comprehensive business and marketing plan for it and went through several rounds of physical prototyping.
I put the idea to bed when I saw there was no way I could ramp up sales volume enough to offset the start-up costs. That decision proved to be wise when the economy went south later that year.
In hindsight I realized what I most enjoyed was the prototyping and iteration process as well as the research required to understand how to bring a product to market in a new industry.