Erasable pens and highlighters

Pilot Frixion pens and highlighters have hard plastic erasers. Rub them over the ink and the writing vanishes. Unlike a pencil eraser that wears away the paper, a Frixion eraser creates heat, rendering the ink invisible. I use them for my paper to-do list, book highlighting, and tabletop gaming.

[image by Simon A. Eugster – Own work, CC BY-SA 3.0]