Throwing Knife is a uncommon Artifact — Equipment card from Magic Origins (ORI), collector number 241. Current market price: $0.12 (foil $0.24), TCGplayer market prices via Scryfall.
Equipped creature gets +2/+0. Whenever equipped creature attacks, you may sacrifice this Equipment. If you do, this Equipment deals 2 damage to any target. Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)