Paralyzer

From SmashWiki, the Super Smash Bros. wiki

The Paralyzer is Zero Suit Samus' Standard Special Move. Its main purpose is to stun opponents, but it also deals some damage. It can also be charged to increase the time an opponent is stunned.

The Paralyzer is also used as her down smash, apparently with a similar effect (although fired downwards).

Interestingly, the stunning effect caused by the Paralyzer is not affected by knockback resistance. Also, Hitting a non-flinch character like Porky with this will cause them to shake like being paralyzed, but will of course still move.

In Metroid: Zero Mission, Zero Suit Samus' part of the game is primarily a stealth game, even with a charge shot, the best she can do with her gun is paralyze Space Pirates for a few seconds.

Zero Suit Samus' Special Moves
Standard Special Move:	Paralyzer
Side Special Move1:	Plasma Whip
Up Special Move:	Plasma Wire
Down Special Move:	Flip Jump
Final Smash2:	Power Suit Samus
1: In Super Smash Bros. Melee and Super Smash Bros. Brawl only. 2: In Super Smash Bros. Brawl only.