Card name: Throwing Knife
Mana Cost: CMC2
Converted Mana Cost: 2
Types: Artifact — Equipment
Card Text: Equipped creature gets +2/+0.

Whenever equipped creature attacks, you may sacrifice Throwing Knife. If you do, Throwing Knife deals 2 damage to target creature or player.
Equip CMC2 (CMC2: Attach to target creature you control. Equip only as a sorcery.)

Expansion: ORIU Origins
Rarity: Uncommon

Throwing Knife
Card rulings (?)
2015-06-22 Throwing Knife's triggered ability triggers before blockers are declared. If you use the ability and destroy the targeted creature with lethal damage, it won't be on the battlefield to block.
2015-06-22 Throwing Knife is the source of the damage dealt because of its triggered ability. For example, you could sacrifice Throwing Knife to deal 2 damage to a creature with protection from red, even if Throwing Knife is equipped to a red creature.