any song that's just a bit more complex and advanced than what you're currently capable of. I'm really not into learning songs (not to say that I don't learn some riffs here and there) I just learn what I want to know from the song and that's it. On guitar Mandatory Suicide is the only song I can play from start to finish and on bass the Super Mario Brothers theme is all I can do on that. I just never got into learning other peoples' music very intimately.