The expression "ace one's sleeve" is sometimes used to indicate the possession of a secret weapon or an unexpected advantage. Synonyms for this phrase could include "trump card," "hidden weapon," "surprise tactic," or "secret strategy." Other related terms might include "joker in the deck," "wild card," "hidden advantage," or "secret weapon." These phrases all connote a sense of power or advantage that is kept hidden until the right moment, suggesting a sense of cunning or strategy. Whether one is playing a game, trying to outsmart an opponent, or simply seeking to gain an advantage in a difficult situation, having an "ace one's sleeve" can make all the difference.