You can always pretend dead? It works with bears,it might with robber,worth a shot at least,lol
OR
pretend to have a seizure of some sort,might scare a guy,at least he won't kill you.
But yea,just ignore advices to get a gun,because if you ain't willing to use it,and you simply can't know that,it will bring you more trouble that good.
Same with knife,just imagine that somehow you defend yourself with knife,and you accidentally kill a guy,you will face charges,and you will probably go to jail,and there,you will be someones prag!
Pepper spray is your best bet if you wanna have something with you.
this 'stick' is also good option if it is legal in your country. You have more reach than with knife,you won't kill a guy(although you might if you want). But yea,it's just safer not to use it,unless you somehow know that guy robbing you doesn't have knife or gun. SInce I highly doubt that you will be experienced enough to be 100% sure that he won't stab you if you try to fight him with your stick. Ofcourse in the hands of trained person,regular joe with a knife wont stand chance against this.
Dunno about availability of tazors ,the ones that you can fire up to few meters just to be safe. Although even regular one when it begins to sparkle and produce it's sound might scare a guy,but I wouldn't bet on it if you are some 'gamer' trying to scare big tough guy.