Holophonor
The Holophonor is a musical instrument in the 31st century and a kind of combination between an oboe and a holographic projector. The music played triggers the projector to show matching holographic pictures, therefore the instrument requires great skill to be played properly, and only few manage some skill in this. Apparently, only a few people in the whole universe can play this instrument, and they are not very good at it.
The instrument is, as it were, instrumental for the plot of two episodes, Parasites Lost and The Devil's Hands are Idle Playthings. In the first episode, the parasitic worms that improved Fry enabled him to play the Holophonor perfectly, which in turn allowed him to win Leela's heart. When he made the worms leave, his new skill was gone and Leela dumped him. Ever since, he tried to reaquire his skill with the instrument, until he made a deal with the Robot Devil and again became a great player in the last episode so far.
It is likely that the Holophonor will play an important role in future episodes and maybe in future comics as well.