I said "it depends". I know me, so I know that I would never intentionally hit anyone with any effort to hurt them unless they struck me first or I actually felt threatened and was trying to get a way out of the situation.
However, I have hit some of my male friends, usually with the back of my hand, on the shoulder or in the chest, for their comments or actions. Most I knew would never hit me back and I only did this to guys I know. One treated me like his sister, so I absolutely always expected to get hit back, but I knew that he wouldn't use all of his force against me. Although, there was at least one instance where I came away with a split lip, but it was an accident and I had started it, so I didn't consider it a big deal. There was one incident however, with a different one of my friends who scared the heck out of me while I was standing watch. I felt someone's hand on my leg and I didn't completely trust all the guys in my division, so it startled me. When the guy came up and I seen that it was one of my friends, I hit him on the shoulder with an open hand and told him that he scared the crap out of me. He then punched me in my shoulder pretty hard. It definitely took me by surprise that he had hit me so hard. I could tell he was mad, but so was I. I felt that he should have warned me before he fixed my pantleg (which is what he had been doing) and he didn't think that it should have been that big of deal for me to have hit him. Our other friends intervened and we worked it out, with each of us apologizing.
So, eventhough I expect to possibly get hit back for hitting a guy, if it is one of my friends and we're just playing or I don't actually punch the guy, I completely expect some restraint if he does hit me back. I doubt that I could hurt any of my guy friends even if I punched them, while many of them could hurt me easily with only a half-hearted punch.