ace up (one's) sleeve

A secret advantage. My stamina is the ace up my sleeve for this race—the other runners don't stand a chance! The defense attorney waited for just the right time to play the ace up her sleeve—a new eye-witness.

Common Names:

Name	Pronounced	Usage
Krystyna	kris-TI-nah	Polish
Raye	[rei]
Panos	-	Greek
Desiderio	-	Italian, Spanish
Lashay	-	African American (Rare)
Etna	-	Irish