"Whether they live or die in the end, nothing like this has ever happened in this island's-several -hundred-year-history. This incident will have an impact on the entire world!..when the battle is over, everyone in the world will be speaking that Straw Hat boy's name! "..
Sanji's speech to Usopp about everyone having a role on the crew and each of them making up for the limitations of the other. Really great after Usopp continued to have doubts about himself due to losing in physical confrontations and feeling weak. Also worked because Sanji, himself, was a liability at times so he had to depend on Nami (to face Kalifa earlier) and Usopp (to save Robin with his sharpshooting at that point in the arc) to accomplish what he wasn't capable of and instead he handles Jyabura which was something beyond Usopp so it really worked with the themes of the arc, revolving around trusting your crew and accepting each other's faults.
Whitebeard's speech at the end of Marineford about One Piece existing was great and still gives me goosebumps when I rewatch it. Zoro's speech to Luffy about the rest of the crew having to respect Luffy and Luffy needing to be resolute and decisive in his decisions was also really good and it's one of the reasons Water 7 was such a great arc and one of the most memorable.