Cheapest priced copy (Ice Age): $0.35 at Card Kingdom, near mint, their price list as of .
Melee 
Instant · Uncommon · Ice Age · #200
Cast this spell only during combat on your turn before blockers are declared.
You choose which creatures block this combat and how those creatures block.
Whenever a creature attacks and isn't blocked this combat, untap it and remove it from combat.
Legal inCommanderLegacyVintage
Not legal inBrawlStandardPioneerModernPauper
1 printing · $0.35 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Ice Age | 200 | Uncommon | $0.35 | — |
2 rulings 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.
- 20 September 2013If a turn has multiple combat phases, this spell can be cast during any of them as long as it's before the beginning of that phase's Declare Blockers Step.