torn between Madara's first death, Deidara's, & Kisame's.
He died as an old cave-man :|
OT: J-man for sure. Who can revive themself from a cardiac arrest with pure will-power alone? Not to mention, J-man had his throat crushed and body impaled by multiple rods, which potentially restricted his movements but whether that was the case or not, he was still able to give it all he got to write a message at Pa's back in a terrible, exhausted state. This happened when he started reflecting on his entire life, and is an example of the notion "to never give up", which is what Naruto, his student, runs on. The flashbacks were perfectly executed.
In addition, his battle was noble and he chose to fight despite having the chance to run from it, which conveys the abnormality of his courage. His death was probably one of the most impactful deaths in the entire series that changed the plot in so many ways. It gave great development to Naruto's character, and it literally saved Konoha from Pain's destruction (from further destruction at the very least) with all the intel and resources that he has provided to them.