Recuerdos de la Alhambra and Capricho Arabe from Tarrega. There are some nice piano versions of them but they are for guitar.
I have tried the Recuerdos. If I was a woodpecker, I would have a chance.
Brahms' transcription of that Bach d minor Chaconne for piano, left hand, is also great. It's a better work out for the left hand than any number of technical exercises, and it stays very close to what Bach actually wrote.
Has anyone arranged it for two hands for those of us who can't manage the left hand version, much less Busoni's? I don't think I have the patience to disentangle the voices and painstakingly input the notes into Finale!
Not sure, but why not just take the left hand arrangement and allow yourself to use both hands whenever you want?
I'm not a great reader, so having the notes already separated into the proper hands would make it easier for me to read and learn it.
Added, thanks to above for the idea of the Recuerdos/Tarrega: never even heard of it, but I think it sounds like fun.