Since it is excluding Roger's execution (the guy who asked about treasure actually started the story)
1) Luffy: Obvious. He defeated the Crocodile which is the first ever effect that lasted till Marineford
2) Ace: Biggest impact. The reason time skip happened.
3) Blackbeard: Well, self explanatory.
4) Whitebeard: Again, self explanatory.
5) Law: That epic cutting moment and alliance with Luffy.
6) Doflamingo: He became the reason for tipping of balance.