I just currently cannot accept that Moriarty is dead. There are a couple theories I am willing to believe...
1. Moriarty faked it.
First of all, Moriarty is all about outdoing Sherlock. It doesn't make sense to me that he would kill himself just to make Sherlock kill himself. Why kill himself with the Game still on??? I would guess that he knew Sherlock would try to "take him hostage" so he made arrangements. Notice that Moffatiss doesn't SHOW us Moriarty's shot, we only hear it. The blood is also excessively fake. With a shot to the skull at that angle there would be spray. Not like a shotgun at close range but he is using a 92FS Inox, a 9mm with decent capability to seriously blow out some skullage, especially as such an extremely close range. And there wouldn't be a trickle of blood There would be far more blood than that. Honestly this is my top theory. And as to why Sherlock "thought" he was dead... Either Sherlock was in shock (my preference) or Sherlock knew, and knew that Moriarty had it all figured out. I prefer the Sherlock in Shock sub-theory because I just happen to really really like it when Sherlock's brain shuts down in fear, shock, or other rush of emotion. Like when Irene played him for him to solve the "code." Anyway I'm off track.
I do NOT accept the theory that Moriarty shot himself but lived. I don't think it's even slightly possible for him to have missed his spinal cord at the back of his throat, and if angled more upwards it would have pierced through the very central part of his brain. I don't believe Moriarty would have chanced that, and even if he did he would not have survived the 5-20 minutes that it took John to get in place. Not possible.
2. Moriarty wasn't Moriarty. I'm not talking body double, I really really hate that theory. I'm saying that someone was pretending to be Moriarty, but the real Moriarty was calling the shots from the shadows. Now I don't like this theory as much because it seems to be that IF Andrew Scott's Moriarty was an accurate portrayal of the REAL Moriarty, then I don't think the Real Moriarty would go through all that. He would want to be seen, he is flamboyant and obsessed with Sherlock and he is not scared.
BUT if the REAL Moriarty has a different personality, then I could see it. He hired someone else to be his face, and the face came along with a different personality.
Now, if Andrew Scott's Moriarty is dead, I would like to see his brother come in. Whether or not you believe that James Moriarty Bro.V.2 was a canonical fact or a Doylian continuity error is your thing. I just want to see another parallel to Sherlock. Jim Moriarty, the younger brother, kicked around (by Carl Powers, by older brother, by god know's who else.), mastermind, dark. But ultimately shadowed by the more powerful, smarter, older brother, Jim Moriarty.
And if none of that is true... I hope Mycroft did it out of love. He's such a little sly, no booty butthead. But he loves with wittle bwuder.
But lets be honest I am 10000% in love with Andrew Scott's Moriarty. I want theory 1 to be true, but I understand why the vast majority of you are like "No he's dead go away."