Monster trio. Easy. They are crewmates, they've fought alongside eachother numerous times, and their interactions are more varied than the others due to having much more panel time together. ASL is really good too, at least the flashback versions. It's pretty cool to see Luffy in more humbler circumstances, not acting as the leader of a trio but as the aspiring underdog. And seeing Sabo and Ace begin to respect and care for the little goof who keeps on proving himself is always satisfying.