Spare Dagger is a common Artifact — Equipment card from Adventures in the Forgotten Realms (AFR), collector number 250. Current market price: $0.20 (foil $0.16), TCGplayer market prices via Scryfall.
Equipped creature gets +1/+0 and has "Whenever this creature attacks, you may sacrifice Spare Dagger. When you do, this creature deals 1 damage to any target." Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)