Flint Missile is a Quick-Play Spell Card.
Spell Cards are usually activated from the hand on your turn unless their type gives another timing window.
On the current TCG and OCG Forbidden & Limited lists tracked here, Flint Missile is Unlimited.
YGOPRODeck lists Flint Missile for these formats: Common Charity, Edison, TCG, OCG, Master Duel.
A listed print of Flint Missile appears in Tactical Evolution (TAEV-EN055) at Common rarity.
Among markets shown on this page, the lowest listed snapshot for Flint Missile is about $0.10 on TCGPlayer (prices change frequently).
