Metroid: Zero Mission
Metroid: Zero Mission is the first game in which the Paralyzer appeared. After defeating Mother Brain, Samus crash lands back on Zebes where she is now in her Zero Suit. Thus her only weapon is the Paralyzer until she recovers her suit.
 Metroid: Other M
Metroid: Other M is the last game to date in which the Paralyzer has appeared. After defeating the final boss, you return to the Bottle Ship to find something irreplaceable. However, you are in your Zero Suit for this part of the game. This object is found later to be Commander Adam Malkovich's Galactic Federation helmet. After this, a self-destruct sequence is initiated, like in many games of the Metroid Series, and you have to race to your ship. However, you are racing to find your ship in your Zero Suit, and the only weapon you have is thus the Paralyzer.