The G.I. Joe character known for using a spear-like weapon and mastering disguises is Lady Jaye.
Lady Jaye is the team’s covert-operations specialist, first introduced in the 1984 toy line and animated series. Her real name is Alison R. Hart-Burnett. Unlike many Joes whose equipment reflects a single military specialty, Lady Jaye is associated with borrowed or replica weapons, including a spear gun, and uses them to imitate enemy capabilities.
Her disguise expertise is equally important. Lady Jaye is portrayed as an accomplished actress and impersonator who can reproduce a target’s voice and mannerisms. This makes her a natural intelligence operative, rather than simply a frontline soldier. Cover Girl and Scarlett are also prominent female Joes, but neither is the character defined by this particular combination of covert impersonation and specialty weapons.