Cheapest priced copy (Amonkhet): $0.35 at Card Kingdom, near mint, their price list as of .
Synchronized Strike 
Instant · Uncommon · Amonkhet · #190
Untap up to two target creatures. They each get +2/+2 until end of turn.
Legal inCommanderPioneerModernLegacyVintage
Not legal inBrawlStandardPauper
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Amonkhet | 190 | Uncommon | $0.35 | $0.49 |
4 rulings from Wizards of the Coast
- 18 April 2017You can’t target the same creature twice to have it get +4/+4.
- 18 April 2017Synchronized Strike can target an untapped creature. It will still get +2/+2.
- 18 April 2017If Synchronized Strike targets two creatures and one becomes an illegal target before it resolves, the remaining target creature will still be untapped and get +2/+2.
- 18 April 2017You can cast Synchronized Strike with two, one, or zero targets.