Semesters have these points where there's a bit of time to kill because of testing. You see some classes more than others or whatever. Sometimes a class gets a lesson they normally wouldn't, or you get an opportunity to do something rather creative. This week not only did we have testing, but we had Spring Break approaching, not an ideal time to wander into new curriculum territory.
By chance I stumbled upon 123D Creature on some website I was reading during the day. At the time it was free, currently it lists for $7.99 which is a bit of a bummer BUT there is value to be had (and you know, buy once, install 15 times). I used it in the context of killing time and giving the kids a chance to do something creative, but you can easily wrap a lesson around it. For example, all the 3D stuff that's in Pre Cal but which comes across a little flat (zing!) because of the limitations of paper. The idea is you create a skeleton, fiddle with joint positions and thickness, and then apply some paint. Once a creature is "cooked" you can chisel out features or tweak it like clay and render it on different backgrounds with funky lighting, etc.
I was pleasantly surprised with how the kids took to it. The room was very quiet for periods of time as they played around, and some of the results weren't half bad. There are also community models from far more talented people that can be downloaded and admired. Super bonus feature if you're an art teacher or middle school teacher or someone who wants to spend more time using it: you can send away for 3D printed versions of your creation.
As this was a one time play day thing, I didn't save a lot of the results, but I was impressed with what they were able to do in 30 minutes. A few got bored, but a small subset was very into it, trying to make a Pikachu or whatever. This is one time where having a stylus available is very handy.