In theory i could be wrong again. if you think some techniques could be used in real life from OP then post it
I think that
#1-Gear 2nd can be used in real life, how you might ask, it may take some training to do that trick, you kinda of have to learn how to control your heart rate (takes years of practice) and you must muster enough stamina to handle it. (yes your body is able to produce steam like luffy does if your heart can even reach such a peak). When you are able to do such a thing be very careful….extremly careful ok your body when it excecsies takes up a lot energy so don't go do what luffy did and go use it for 20 minutes..you'll probalby end up dead
#2 Sanji's kicks-are a form of kick boxing called brazilian kick boxing (except without hands)
#3 Ussops sniping
that's all i could come up with
anything else you guys can come up with