I used FreeCAD (V .15, Win 7) to develop the design for a newly-patented floating koozie. It uses a pivoting ballast arm to keep a drink upright in the water. The arm then folds up so it can sit flat on land. After 64 iterations of the design in FreeCAD, and a number of 3D prints, the design is ready for the market!

It's been fun to use the project to get up to speed with FreeCAD. I still struggle with the Parametric concept sometimes. Such as subtracting copy of a complex object with many dependencies from another object, and ending up with an exponentially-growing number of dependents and a massive file size...but I'm getting better!
I've 3D printed the most recent design and it works!!

I have used it as a prototype displayed in my Kickstarter campaign. More pictures and info are there:
https://kck.st/2Ui2UkW
I posted it to the FreeCAD subreddit and it was suggested I post here!