The one time I did fight my friend, we were both playing with underpowered spring guns and he shot me, accidentally from about 10 feet away, with a plastic bb right on the tip of my nose. It couldn't have been more than 150 FPS, maybe 175 tops, but it still stung for a good long bit.
My cousin also shot me point blank in the arm with a gun he thought was unloaded and unroostered. That left a mark.
At my last party, which was... a week ago (Wow... Seems a lot longer than that) It was my friends Steven (The host), David, and I vs my friends Nathan (Who went over the top modding his sniper. He bought a $150
trigger and a super strong spring that ended breaking his gun), Christian, Austin and Matt (They had the most powerful guns there). So I was walking around with my little CO2 pistol, annoying Austin and Matt till they chased me away and I had to hide in some woods for a while. When I came back, everyone had teamed up against David. So I ran over to Austin and ask him why they did it, and he replied, "Because we felt like it. :D". Then he told me that both Matt and he and been "Dry firing" for pretty much the whole time because they forgot to bring BB's with them. So me, still being on David's team, stood inbetween Matt and Austin and shot them both point blank in the back of their legs with my 325 CO2 gun. Then I ran away before anyone else could shoot me.
For those who said, "TL;DR":
I shot my friends in the back of their legs and made them bleed.