Divided between 1 and 4. One is a mile stone of the manga, it sets a lot of things. It is also the main villain with the 3 protagonists. Number 4, Ace dies, has less value for the story compared to the 1st but it is scene that hits you like a truck. Very emotional (and unexpected even at the time, Oda used to do way less fake deaths but it was still really something unexpected). Still for the story the most important is the 1st.
About the others they are just minors. Roger laugh is way in in the manga, almost the end pretty much, also it adds to the mystery of the OP but really not something really epic.
Luffy punching the CD was something which was charged up in the whole arc but in the end it is repetition of Usopp burning the WG flag in Enies lobby. They already were sworn enemies and that was just to underline Luffy and co are coller than the other pirates cause they had the balls to attack CD (that also brought to their demise in the end).
The death of WB was epic but it was expected since his introduction, the badass old guy that loses his life while kicking ass, there is something like this in every manga (but OP did this really really good), but not so iconic like the others. Maybe he telling the OP exists had more value.
The last one was epic as a Zoro fan but that is a totally Zoro scene, cool and all but 1 and 4 are mile stones of the manga. This can be compared to WB death to a degree.