Ax Bass

The Axe-bass is an heirloom of Marceline's family. It was originally a battle axe before Marceline converted it into a bass guitar, which Hunson Abadeer calls "some kind of lute." It makes its debut in "Henchman," where Marceline plays and sings the "Fisherman Song" for the Second Nut Son. Later, she orders Finn to kill the Dimple Plant Monster with it, but he refuses. In the episode "It Came from the Nightosphere," she plays the "Fry Song" with the bass. When Finn summons her father, Marceline's dad seems surprised that Marceline has it and takes it from her. In her efforts to reclaim it, she is shown to care somewhat more for the bass than she does for Finn, as she chooses to save it from hitting the ground rather than Finn. It shows up in "Go With Me," where she was about to play it, until Finn interrupted her by his singing outside her house. It appears again in "What Was Missing" when she plays it during the songs "I'm Just Your Problem" and "My Best Friends in the World." " It makes an appearance in the episode "Marceline's Closet," where Marceline plays it in "Journal Song." Its latest sighting was in the episode "I Remember You," Marceline is briefly seen strumming on it before the Ice King enters her cave, she later plays it during the second half of "Remember You." Marshall Lee's Axe-bass appeared in "Bad Little Boy." He used it to accompany the song "Good Little Girl."

Design
It is an entirely red (except in "Henchman" the edges are silver), double-sided battle axe with two chips on the right side. Such axes, namely the labrys, are a symbol associated with feminism and gender equality. The head stock was most likely added by Marceline, along with the machine heads, two on each side. The pickups, also added by Marceline, appear to be single coils of unknown manufacture. The body has just two knobs (for volume and tone).

Marshall Lee is shown playing a variation of the Axe-bass in the intro to Fionna and Cake episodes, however in "Bad Little Boy," he plays what may be an Axe-guitar, as it has 6 tuning knobs for 6 strings. His Axe-guitar has a head stock shaped like a skull and one blade.

Trivia

 * In "Henchman," the bladed ends were silver. However, in "It Came from the Nightosphere," they were red.
 * In "It Came from the Nightosphere," the Axe-bass is referred to as both a bass and a guitar.
 * Marceline's Axe-bass is highly similar to The Bloo Superdude's guitar in Foster's Home for Imaginary Friends' "The Bloo Superdude and the Magic Potato."
 * Somehow the Axe-bass can be clearly heard in "It Came from the Nightosphere" when Marceline sings the "Fry Song," even though it isn't plugged into an amplifier. This can also be observed in later episodes including "What Was Missing." This is most likely because the bass is enchanted.
 * It is unknown whether the Axe-bass has a truss rod, which curves the neck so that the strings do not lay flat against the fingerboard, although the neck must be curved somehow for Marceline to be able to play it.
 * It is one of three basses that Marceline owns, the other two being the bass in "Evicted!" and the Butterfly Bass in "Heat Signature."
 * It's been mentioned that is was used to kill someone, but it is unknown if it is true, or who was killed. It is possible that this person was the Vampire King.