xkcd - Hand Sanitiser

20,000 for those who can't be bothered working it out.

Predictor: Pregnancy tests

[Couple with the 'father' standing behind an obviously pregnant 'mother' both looking happily surprsied at a pregnancy test]

[Box of 'Predictor']

When you want to be sure.

A must-have item to see if you're pregnant, even when if it's painfully obvious that you are - indeed - pregnant.