Cheapest priced copy (Rivals of Ixalan): $0.35 at Card Kingdom, near mint, their price list as of .
Hornswoggle 
Instant · Uncommon · Rivals of Ixalan · #39
Counter target creature spell. You create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.99 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Rivals of Ixalan | 39 | Uncommon | $0.35 | $0.99 |
One ruling from Wizards of the Coast
- 19 January 2018Hornswoggle can target a spell that can't be countered, such as Nezahal, Primal Tide. When Hornswoggle resolves, that spell won't be countered, but you'll still get a Treasure.