Shredder for comminuting various materials, comprising: at least one rotor which is rotatable about an axis and which has an outer peripheral surface extending about said axis; a plurality of knife holders which are fixed to the outer peripheral surface of the rotor at locations which are spaced from each other in the peripheral direction and axially along a length of said rotor; a plurality of knives (130, 230, 330) which are mounted on said knife holder; a stationary counter knife which is mounted adjacent to the outer peripheral surface of the rotor and extends over the length of said rotor, wherein the counter knife defines a plurality of generally V-shaped grooves which are spaced from each other along said counter knife, wherein each generally V-shaped groove is oriented to at least one of said knives (130, 230, 330); wherein each knife (130, 230, 330) has a rigid body having a configuration when seen in a first direction, wherein each knife (130, 230, 330) is mounted on a respective knife holder and the first direction is oriented substantially tangentially to the outer peripheral surface of the rotor, wherein the body defines a corner (134, 234, 334) which is formed complementary to a respective one of said V-shaped grooves in the counter knife, wherein the knives (130, 230, 330) are mounted in an orientation such that the corners (134, 234, 334) mesh with the respective V-shaped grooves upon rotation of said rotor about said axis; characterized in that at least some of the knives (130, 230, 330) are those which have several cutting points (140a, b; 240 a, b c; 340 a, b, c, d) in which the corner (134, 234, 334) of the knife (130, 230, 330) defines a plurality of cutting points (140a, b; 240 a, b, c; 340 a, b, c, d) spaced from each other along said first direction, wherein said plurality of cutting points of each knife (130, 230, 330) having several cutting points is arranged in such a manner that during the rotation of the rotor, said cutting points (104a, b; 240 a, b, c; 340 a, b, c, d) sequentially mesh with the respective V-shaped groove. at least one rotor which is rotatable about an axis and which has an outer peripheral surface extending about said axis; a plurality of knife holders which are fixed to the outer peripheral surface of the rotor at locations which are spaced from each other in the peripheral direction and axially along a length of said rotor; a plurality of knives (130, 230, 330) which are mounted on said knife holder; a stationary counter knife which is mounted adjacent to the outer peripheral surface of the rotor and extends over the length of said rotor, wherein the counter knife defines a plurality of generally V-shaped grooves which are spaced from each other along said counter knife, wherein each generally V-shaped groove is oriented to at least one of said knives (130, 230, 330); wherein each knife (130, 230, 330) has a rigid body having a configuration when seen in a first direction, wherein each knife (130, 230, 330) is mounted on a respective knife holder and the first direction is oriented substantially tangentially to the outer peripheral surface of the rotor, wherein the body defines a corner (134, 234, 334) which is formed complementary to a respective one of said V-shaped grooves in the counter knife, wherein the knives (130, 230, 330) are mounted in an orientation such that the corners (134, 234, 334) mesh with the respective V-shaped grooves upon rotation of said rotor about said axis; characterized in that at least some of the knives (130, 230, 330) are those which have several cutting points (140a, b; 240 a, b c; 340 a, b, c, d) in which the corner (134, 234, 334) of the knife (130, 230, 330) defines a plurality of cutting points (140a, b; 240 a, b, c; 340 a, b, c, d) spaced from each other along said first direction, wherein said plurality of cutting points of each knife (130, 230, 330) having several cutting points is arranged in such a manner that during the rotation of the rotor, said cutting points (104a, b; 240 a, b, c; 340 a, b, c, d) sequentially mesh with the respective V-shaped groove.