I don't want to hear about "It's a gag" or whatever. Usopp is beating up Luffy with his fists, you see marks on Usopp's fists, and yet even though Luffy is made of rubber and immune to blunt attacks, Usopp has damaged him and drawn blood with punches.
Gags are real in one piece, as proven 6 chapters later when Sanji almost dies from a nosebleed and needs a blood transfusion. Usopp armament haki confirmed.
