i've always thought the rasengan WAS the unfinished jutsu. remember when Jman and naruto were in the noodle shop and those thugs were acting up? that's the first time we saw the rasengan, when Jman used it on the thug and naruto got all excited and wanted Jman to teach it to him. during their training Jman explained to naruto that it was a technique that the 4th made up but that it was unfinished. the rasengan alone is just chakra manipulation but for it to be a complete jutsu it needs to have element added to it. Jman taught naruto the rasengan and told him to "make it your own". that's what naruto was working on while training with those thousands of shadow clones. remember he was trying to learn how to better control his wind element? cutting the water fall and everything. anyway, he came back from that training with the rasenshuriken. the 4th might've gone a different way with it. i assume different characters could've finished the jutsu different ways and the rasenshuriken was how naruto handled it. that's just how i remember it. now that he's learning nature energy i wonder if he'll try to find a way to incorporate that into his rasenshuriken. i'd still like to see him throw it but that might be too DBZish...
that's not to say that the 4th couldn't have had more than one unfinished jutsu. maybe he had a few that were unfinished, who knows?
if i'm wrong please correct me... i wish i had time at work to find the pages i'm seeing in my head but i don't so i'm just going off memory.