There is documentation of assailants that left a would-be-victim alone after she told him that she was pregnant and it would kill her baby. (Some case were women that were too old to even have a baby.)
Telling an attacker that you have VD or AIDS can discourage him.
It may sound disgusting, but putting your fingers into you throat and making yourself vomit usually gets results. (This method is not often used except as a last resort.)

useful defense weapons.

nail file
rat tail comb
teasing brush
pens and pencils
keys
anything rigid

Or just bend over and kiss something goodbye….