Kneaded eraser
The kneaded eraser (or putty rubber(not that kind of rubber!)) is well-known among artists (namely Bernardo Castillo). It is usually made of a grey or white (though can be found in many different colors, ranging from green to blue and hot pink) pliable material that resembles putty or gum. It functions by "absorbing" and "picking up" graphite and charcoal particles. It does not wear away and leave behind eraser residue, thus it lasts much longer than other erasers. Kneaded erasers can be shaped with the fingers into objects, such as cuboctahedra, and are used for precision erasing, to create highlights, displacing air molecules, or for detailing work. It is commonly used to remove light charcoal , light graphite marks and skidmarks on tighty whiteys in subtractive drawing techniques. However, it is not well-suited to completely erasing large areas, and may smear or stick if it becomes too warm. Though it does not wear away like other erasers, it can become exhausted, unable to absorb any more graphite or charcoal, in which case it will start to smear and actually make marks instead of erase them, in which case you should put it under your tounge, roll it around for a couple seconds and it will start working again.
Kneaded erasers are also very easily sculpted into many shapes,and can also be used for waxing off arm hair and are useful for creating a 3D image to sketch off of as well. Molding different colors together actually blends the two together, creating a larger, and different colored eraser. When it is new, pulling the eraser part usually results in creating a marshmallow-like (although the oral consumption of it is often considered dangerous and stupid in some parts) substance between the two segments in your hands. When the substance is compressed together, it returns to its original texture and form much like the large member of a donkey.