Adding lights to random things in your house is great fun for kids of all ages. Adding solar lights to random things in your house is even more fun. Adding red eyes to a piggy bank to make it evil is probably the most fun you'll have all afternoon.
I found this piggy bank at my local Dollar Store and instantly knew he'd look great with evil red eyes. I could have gone the simple route and wired the eyes to a power adaptor, but where would the fun be in that?
In the end I made a simple light detecting solar circuit that fits inside the pig. I'll stick him in my classroom next week and see if the kids notice him.
This is cheap to put together, easy to build, and long lasting. (Also, you don't have to stick this circuit into a pig. It'll work with anything.)