An end effector (8012, 22090) for fastening tissue, comprising: a cartridge (810, 22000) comprising a longitudinal row of staple cavities; a plurality of staples removably stored in said staple cavities, wherein each said staple comprises: a base; a pair of legs extending from said base; and a plane formed by said pair of legs, wherein at least one of said legs comprises at least one barb extending circumferentially around said leg for less than 360 degrees and extending beyond the plane formed by said legs such that the barb extends within and outwardly from the plane formed by said legs, and wherein each said leg comprises a tip configured to pierce tissue; an anvil (8014,10060) configured to deform said staples; a plurality of staple drivers movable within said cavities configured to lift said staples toward said anvil; and a firing member configured to lift said staple driver system toward said anvil, wherein said firing member comprises a first portion configured to engage said anvil and a second portion configured to engage said cartridge, and wherein said firing member is configured to relatively position said anvil and said cartridge, wherein the barb includes a first surface and a second surface which extend from and around a portion of a perimeter of the staple leg and extend beyond said plane formed by the staple legs, wherein the first surface and the second surface converge at an edge that is arcuate. a cartridge (810, 22000) comprising a longitudinal row of staple cavities; a plurality of staples removably stored in said staple cavities, wherein each said staple comprises: a base; a pair of legs extending from said base; and a plane formed by said pair of legs, wherein at least one of said legs comprises at least one barb extending circumferentially around said leg for less than 360 degrees and extending beyond the plane formed by said legs such that the barb extends within and outwardly from the plane formed by said legs, and wherein each said leg comprises a tip configured to pierce tissue; a base; a pair of legs extending from said base; and a plane formed by said pair of legs, wherein at least one of said legs comprises at least one barb extending circumferentially around said leg for less than 360 degrees and extending beyond the plane formed by said legs such that the barb extends within and outwardly from the plane formed by said legs, and wherein each said leg comprises a tip configured to pierce tissue; an anvil (8014,10060) configured to deform said staples; a plurality of staple drivers movable within said cavities configured to lift said staples toward said anvil; and a firing member configured to lift said staple driver system toward said anvil, wherein said firing member comprises a first portion configured to engage said anvil and a second portion configured to engage said cartridge, and wherein said firing member is configured to relatively position said anvil and said cartridge, wherein the barb includes a first surface and a second surface which extend from and around a portion of a perimeter of the staple leg and extend beyond said plane formed by the staple legs, wherein the first surface and the second surface converge at an edge that is arcuate.