Most modern games offer in-game features that add to the overall experience in ways that have nothing to do with the game or the mission itself. One such feature is the whiteboard used in Duke Nukem Forever. While the game itself was met with a certain level of criticism and the advertising agency working with them failed even more, this feature of the game has brought out some amazing creativity in people.
Check out this video putting a little nibble from another popular game into this one. Pretty epic.
Other materials besides rubber may be used to produce a stamp. Woodcut and linocut, The carving of linoleum, are art forms based on the same principles. Linoleum is much harder than rubber and thus requires special tools.