As shown most dramatically in "Granite State," Walt wants all that he's done to actually mean something. I'm almost certain the machine gun is for the Nazis. Not sure who the ricin is for--Lydia? Jesse? WALT JR's PANCAKES?!--but I'm fairly certain the climax of the show will center in some way around the conflict between Jesse and Walt. I'm not sure how that will all shake out, but... that still leaves the falling action and the resolution... and an important loose end.
The blood money.