Grimace

From RayWiki

The Grimace is Rayman's initial line of defense, which he has been able to do right from the beginning in the original Rayman. It's where he basically makes a funny face by holding his mouth wide open with his hands, used to scare enemies that are in his way and cannot defeat yet. This is sometimes replaced with other temporary powers he later gets in the game, such as the Magic Seed, but it is permanently replaced by running at a late point in the game.

In Rayman 2 and the Gameboy Advance version of Rayman 3, Rayman only pulls this off while he is being left idle.

In Rayman 3 however, he is bestowed this power by Gumsi after defeating Reflux in the Desert of the Knaaren, which he uses to convert Black Lums back to Red Lums by scaring them after defeating a Hoodlum. It is known as the Power of the Leptys in this game.