Levonorgestrel
"If you're here reading these comments, that means you're a boy or girl in the same position I was:  A mistake was made somewhere and you're concerned about pregnancy.  The waiting is gruesome, but I'm here to assure you; this pill works.  After ingesting the pill 16 hours after sex, a period of terrible waiting began.  My girlfriend and I were both antsy and scared, and the time of her expected period came and went.  She was 8 days late, but alas, she had it.  This pill works in mysterious ways that can cause a later period, but I'm here to tell you there is nothing to worry about.  It's scary, it's unsettling, but I'm here to tell you to calm down and relax because this pill will take care of everything."