Cheapest priced copy (The List): $0.69 at Card Kingdom, near mint, their price list as of .
Tail Swipe 
Instant · Rare · Store Championships · #15
Choose target creature you control and target creature you don't control. If you cast this spell during your main phase, the creature you control gets +1/+1 until end of turn. Then those creatures fight each other. (Each deals damage equal to its power to the other.)
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
4 printings · $0.69 to $0.79 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Dominaria United | 182 | Uncommon | $0.79 | $0.79Out of stock |
| Foundations Jumpstart | 721 | Uncommon | $0.79 | — |
| The List | DMU-182 | Uncommon | $0.69 | — |
| Store Championships | 15 | Rare | $0.79 | — |