Being a gamer girl (well, now "gamer woman" if something like that exists) I know that strange situations can arise and I also know that many women don't dare to say anything in such situations for fear that by "rejecting" the man they might cause aggression on his part. They just don't dare to be confrontational.
And I believe that's a mistake.
Look the guy in the eye, smile, and say "This is too close for me and I don't like to be touched this way."
Sadly many women still haven't learned to do that. But it works like a charm in most cases. And if it doesn't you can still freak out, lash out and alert security.
Don't even smile. If you smile, there's always that chance you'll accidentally come off like you're testing him or flirting, especially if he's into PUA or if he's drunk. The clearest way to communicate that you don't want to be touched/bothered is just by looking him in the eye and stating in a stright-up no-nonsense manner, "Please don't touch me." or "Please leave me alone." Make sure there is as close to zero chance of misinterpretation as possible if you genuinely want the guy to stop doing whatever he's doing. Don't be rude about it, just make sure the message is clear and you're not giving any contradicting signals.
Or perhaps rather than being ridiculous, we can recognize that women are also contributing to the problem here.
Men are expected to hit on the women, which means that we're expected to be able to figure out the difference between a friendly smile, and a flirting smile. The difference between a coy hair flip and just wanting to get the hair out of the face. Figuring out when the woman that's flirting with us is interested, and when she just wants us to do something for her.
The way you put it, trivializes just how dangerous it can be approaching women. The response we get, is often times completely random and unpredictable. And a sexual harassment complaint, even with out merit, can easily wind up with us being out of work, or sued.
This here is a good example of what I'm talking about: http://seattletimes.com/html/opinion/2021142903_daniellecampoamoropedxml.html
She's literally suggesting that men behave in a way that's extremely dangerous for us, and likely to wind up with her being married to somebody that likes hitting women.
We're getting chewed out for being more respectful and not magically knowing which women are actually interested in us.
But, ultimately, women are far, far worse when it comes to men. There's nothing that a man can do that can come close to the damage that women do via paternity fraud. Which as far as I can tell occurs in about 3-4% of pregnancies in the US according to the wikipedia.