Slam the base of the palm of your hand into the bottom of your attacker's nose. I mean, hard -- like you want your hand to come out the back of his head (it's called "punching through the target"). You WILL disable him, and you might very well kill him.

Don't bother with a knee or kick to the crotch -- all he has to do is turn ever so slightly and you'll knee or kick his leg. Instead, very forcefully grab upwards between his legs, grab whatever you can, and while holding VERY tightly yank downwards, twisting as you do so.

If you must strike with your hand, hold something hard -- a lighter, a short thick stick, a tube of lipstick -- in such a way that it sticks out above the top edge of your fist and hit with that. NEVER hit with your fist (unless you've been properly trained to do so).

Never submit. Fake it, if you must do so to get a chance to attack. If it's money they want, give it. You can replace things, you cannot replace yourself.

I know of a woman who quite literally ripped the testicles off a rapist. She handed them to the police, who found him in the local Emergency Room. (Yes, he was a rapist -- he'd attacked others but this time, well....)