My dream is having such a magical guitar that would rearrange the songs I perform in different tonalities, in accordance with my mood. It would simply tune its strings minor/major accordingly.
For example, when playing cheerful La Cucaracha being in a sad mood I would hear its melancholic D-sharp minor version. And vice versa, when performing tragic classics like Albioni's Adagio being in cheerful mood I would hear it in a funky major key.

I would love to experiment rearranging different musical pieces this way