Thought this looked unusual & useful, if your kids are anything like mine, they are obsessed with stationery & school kit, I know they would LOVE this & for once it's not scented / sparkly / pretty but impracticable (like so many of their erasers).
Crayola 3-in-1 calculator, ruler and stencil
The ruler is 12 inches and folds out. It also has 3 holes, allowing you to store it in any 3-ring binder. The stencil offers a variety of shapes and sizes, ideal for enhancing projects.
They have a few other offers too, will pop links in 1st post