Arya ending the War (Spoilers extended)
The good ol' question was:
What if Arya had given Jaqen different names for her three free kills?
In this scenario, for example, she chooses Tywin, Joffrey and Tommen as a way to try to end the war and give Robb a better fighting chance.
With Tywin gone, Kevan would've taken over control of the Lannister hosts,
With Joffrey and Tommen gone in maybe one night, Cersei would've fallen more and more into paranoia and unwise decisions but no Tyrion trial would've taken place, most likely.
Without Tyrion facing trial he doesn't leave and remains at the Red Keep, as new possible candidate as Lord of Casterly Rock depending of Jaime's current situation in his Kingsguard role, probably shielded also by Kevan,
Cersei tries to keep Myrcella closer still and perhaps raise a claim, but without two male heirs the Crown and Small Council would've most likely decided to find and name another male one and, if underage, a regent that is not Cersei.
Who would be the new heir?
Who would be the regent?
Would the war had ended completely or the Lannisters would've kept it going until absolute defeat, or absolute victory?
Would have Varys seen the need to intervene now and kill Kevan or Cersei or even Tyrion?
And, ultimately, would have Arya made things better or worse for the Stark-Tully faction?