I have always been a little crazy, so do not be shocked by my answer:
My very first martial arts instructor taught me a very interesting multi-attack technique:
He asked, "What do you do when multiple persons attack you?" I said..."RUN!" He said, "No, the chance one is faster than you is too high." I said, "kick one in the balls" He said, "NO, the pain passes to quickly and the others will get even madder as they think only a weak person would do it and they will just kick the shit out of you more" I asked, "Well, what should I do!?" He Said, " pick out the biggest guy, and poke out his eye while focusing all your energy with loud ass Ki-ya...(while screaming)" I was like, "What!?!?" He said, " the chances that all the others look at the guy with his eye all fucked up and think..."HOLLY SHIT!!!! And, run away faster than the speed of light....Your fight will go from many to one really disabled guy that is allllllot of pain... and you might want to finish him off so you do not have to look over your shoulder the rest of you life"
I usually start by telling them in a very straight face, if you do not leave me alone, I will, at the very least, be trying to kill one of you...you may kick my ass, but I WILL kill one of you... two different games...you may win your and kick my ass, but I WILL win mine"
Then I ask do you still ant to play?
It is funny, I have never had anyone answer "yes", nor continue to physically bother me... I usually get a dumb ass responce like." oh yeah sure you will, what a tough guy...blah, blah blah,... but I just continue to look at them very calmly and seriously... as the walk away talking shit....
One note, I have no desire to hurt anyone, but I would not hesitate to keep my word... the world has very wonderful things in it (mopeds!!!), but it can be really dangerous... and when it comes down to it... I will not allow some jack-a-mo to be physical with me... they could easily seriously hurt you or even kill you by accident... so be honest and up front with your intention to fucking kill them if they continue to play games with your physical being. It also, helps to get some training as those type of people generally only pick people to mess with that in some way look the role of victim.... Training gets rid of that quickly as you carry yourself differently. I looked that way for may years without knowing it.... I still do some times, and some one starts in..but quickly realizes that I am not that guy.
Good luck to you and get some martial arts training... it is really healthy and helps a lot.