One of my projects at the moment is trying to work out how to use a laser cutter to seal together sheets of material, and cheap ways of laser etching onto metals. I have also recently seen a nutter, HERE, laser etch his fingernails by disabling the safety catches on a laser (note the burned and scarred edges of his fingers before you think this is a good idea!). these are all interesting but sometimes it is the super simple that has the most chance to educate if the learnign goes beyond just the skills to make it.
This keyring design below is a straight forward laser project cut in 3mm acrylic with a 2mm ball bearing inside. It is very cheap and quick to make, can be prototyped in cheaper materials and produces a high quality finished product that would be easily saleable. Provided you go beyond merely designing around a standard pattern, and ensure there is work and progression onto mazes themselves, industrial standard material sizes, opportunities to try multi level mazes (3 stacked on top of each other?) etc.. then this would be a good project.
IF you find yourself knocking out the same old size keyrings and ideas, each barely discernible from the rest, and a good way to tell is whether students need to put their name on them to know which is which, then contact me for some tips!