I had 1 mill the other day. Since I rarely play anymore, I decided to try spend it all and see what I got. My conclusion:
1) Opening so many item box's one after the other was a complete drag. I gave up halfway through because of how long it was taking me.
2) After 500,000 SM I managed to get 3 mythical items. 1 shotgun and 2 tappings legs.
3) None of the items I got are ones I will ever use
4) It took me another hour to fuse all these items in to one of my weapons. Including the power kits I managed to get, I managed to complete 1/10th of the power needed for a level 9 needle blaster.