Used the Voronoi Skull model to create a real CLASSIC piggy bank that requires you break it open to get your money! Should only cost a dollar or two in material so it's worth it. Added a few more bars on the bottom of the model to keep coins from falling out the bottom. Also, cut a slot out of the top so you can drop coins into. There may still be a few holes in the skull that are big enough to let US quarters through, quite a few more that could allow dimes through so beware! I only save quarters in mine so that it's a bigger payday when it comes time to break it open!
When I print this I always sink it about -1.5 mm lower into the bed in order to get more surface area to touch the bed, but I've also printed it as is after centering with Simplify3D. Whoever created the original model also included supports in the model and they've always worked great for me. So no added supports or rafts needed. It can get stringy so tune your printer's retraction and temperature settings well. I've played around with infills from 30 - 100% looking for a good strong print but haven't noticed a huge difference. If you're a pro let us know your thoughts in the comments. Good luck printing!