Opening Gambit boosts mobility for about the first 30 seconds of a match; in Splatoon 2, that amount of time can be extended by splatting an opponent or assisting a teammate in splatting an opponent. This ability is restricted to headgear as a main ability, and cannot be rolled as a sub ability.
The ability is ideal for reaching objectives before opponents during the start of the match, gaining a tactical advantage.
Mutual exclusivity
This ability is found as the main ability only on headgear, so other abilities found only on headgear are mutually exclusive with it; in other words players cannot have them together. These abilities are Comeback, Last-Ditch Effort, and Tenacity.
The ability is active for about 30 seconds starting from the start of a match. While the ability is active, that amount of time is extended by about 7.5 seconds for each splat and assist the user is credited with.