My son is really into the small wooden trains, like the thomas the tank, or the Brio ones. I saw the MTA had some modeled after the NYC trains but they seemed a bit over priced and no detailed at all.
So I decided to make my own. There were modeled from several pictures, they are fully compatible with wood tracks and other trains that use magnets to connect. I was able to model a connector that uses a magnetic ball to connect to other trains, since the ball is loose within the container it can swivel around in any orientation and connect to all trains models in any orientation (Shown Above)
I love these headphones, they give great sound and are comfortable. I liked it so much I bought a pair for my wife as well. I used them daily until the hinge broke and I found out it was a relatively common issue with this model. So again 3D modeling and printing to the rescue.
I spent about a month measuring, modeling, printing, testing until I got it just right. Worked so well I bough a pack of 4 broken ones and fixed them all.
This I designed for my son when he was 2 years old. At that time he was really into the Little Einsteins cartoons, I wanted to get him the rocket to play with but the toy had been discontinued and any available were very expensive.
So I started up Solidworks and designed this for him. I then printed it and he played with it almost every day. Until he lost it then I printed it slightly bigger and in red. He loved it even more.