Elasticity

Summary
Elasticity is the ability to stretch, elongate, flex, and twist, and otherwise manipulate one's body into impossible shapes for various purposes. The limits and applications of this ability vary from user to user, and it may sometimes grant them additional properties akin to other elastic substances. Particularly skilled users can emulate Shapeshifting by molding their bodies into the forms of others.

Users
Mister Fantastic (Marvel Comics)

Monkey D. Luffy (One Piece)

Franmalth (Fairy Tail)

Piccolo and Majin Buu (Dragon Ball)

Various Aliens (Ben 10)

Martian Manhunter, Plastic Man, Elongated Man, and Madame Rouge (DC Comics)

Mrs. Incredible (The Incredibles)