Headlight for a Tricycle
This is a headlight I built for my son's tricycle. It is designed to fit a fisher-price plastic tricycle, but you can tweak the designs (in openSCAD) to mount it on any kind of tricycle you like. It is perfect for riding in the dark, and my son absolutely loves it.
Full instructions and pictures here: http://www.jasonthalken.com/2014/11/build-project-headlight-for-tricycle.html