Punch/slap you. Or if it's extremely weak. Laugh at you,insult you and then ignore it. If you attempt to do it again i'll grab you hand to stop you from slapping me.
Damn everybody be answering they'd retaliate back or smth :v
I'm p weak physically so i have my ways when dealing w/ these things.
I'd either yell out "sexual harassment" if it's in public or just use some pepper spray if no one's around.