Cheapest priced copy (Ice Age): $0.35 at Card Kingdom, near mint, their price list as of .
Gaze of Pain 
Sorcery · Common · Ice Age · #128
Until end of turn, whenever a creature you control attacks and isn't blocked, you may choose to have it deal damage equal to its power to a target creature. If you do, it assigns no combat damage this turn.
Legal inCommanderLegacyVintagePauper
Not legal inBrawlStandardPioneerModern
1 printing · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ice Age | 128 | Common | $0.35 | — |
One ruling from Wizards of the Coast
- 15 April 2013An ability that triggers when something “attacks and isn’t blocked” triggers in the declare blockers step after blockers are declared if (1) that creature is attacking and (2) no creatures are declared to block it. It will trigger even if that creature was put onto the battlefield attacking rather than having been declared as an attacker in the declare attackers step.