Cheapest priced copy (Khans of Tarkir): $0.35 at Card Kingdom, near mint, their price list as of .
Dragon Grip 
Enchantment — Aura · Uncommon · Khans of Tarkir · #107
Ferocious — If you control a creature with power 4 or greater, you may cast this spell as though it had flash. (You may cast it any time you could cast an instant.)
Enchant creature
Enchanted creature gets +2/+0 and has first strike.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Khans of Tarkir | 107 | Uncommon | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 20 September 2014You must cast Dragon Grip at the latest during the declare blockers step after blockers are declared if you want first strike to matter during that combat.
- 20 September 2014If you're using Dragon Grip's ferocious ability to cast it as though it had flash, you must control a creature with power 4 or greater only as you begin the casting process and put Dragon Grip on the stack. Losing control of that creature while casting Dragon Grip (perhaps because you sacrificed it to activate a mana ability), or in response to Dragon Grip won't affect Dragon Grip on the stack.