Kneaded eraser
The kneaded eraser (or kneaded rubber eraser) is well-known among artists. It is usually made of a grey or white (though can be found in many different colors, ranging from green to blue) 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 and used for precision erasing, to create highlights, or for detailing work. It is commonly used to remove light charcoal and light graphite marks 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.
Kneaded erasers are also very easily sculpted into many shapes, 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 substance between the two segments in your hands. When the substance is compressed together, it returns to its original texture and form.