Cheapest priced copy (Dragon's Maze): $0.35 at Card Kingdom, near mint, their price list as of .
Showstopper 
Instant · Uncommon · Dragon's Maze · #102
Until end of turn, creatures you control gain "When this creature dies, it deals 2 damage to target creature an opponent controls."
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dragon's Maze | 102 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 15 April 2013Creatures that come under your control after Showstopper resolves won’t have the ability.
- 15 April 2013If another player gains control of a creature you control after Showstopper resolves, and then later that turn that creature dies, the creature’s controller when it died controls the triggered ability. That player chooses a creature that one of their opponents controls as a target.