Breaking Bad Ending Theory 1: (SPOILERS DONT READ IF YOU DIDN'T SEE OZYMANDIUS)

It is possible that Walt will in fact, partially, redeem himself. Here is how it might go down. Walt, perhaps finally broken and alone finds out that his family is in peril and Jesse is being held prisoner, will come back and buy the machine gun ready for a final stand off with the Aryan Brotherhood to free Jesse and get his money back. Now, since Jesse knows the truth of Walt watching Jane die, Walt will given the ricin to Jesse to poison Walt with - a sort of taking responsibility, but also...