The whole point of mini company is to come up with your own idea that's authentic and unique. You really need to think outside the box to make your idea/product interesting while still achievable. I think making it doable and efficiently doable is key to it being successful.
I haven't mostly because people don't bother with it so they never got a chance to succeed from the start really. It's a worthwhile project if you put in half an effort. My team of two didn't win anything but still made a nice profit of over 500 euro between us!