We had a little K'Nex factory churning out "quarks" and "bots" today in Advanced Algebra. I used this activity to introduce linear programming in a non-threatening way. It also turned out to be perfect because we had a modified schedule (which I'd forgotten about over the weekend), so our class periods were much shorter than usual and this took up the perfect amount of time.
I was surprised just how few of my students had ever seen or used K'Nex before. One student asked me if I'd made a typo on the handout and had meant to write "Kleenex" instead of "K'Nex."