Here is a website dedicated to trying to find out what is the worst sound in the world: http://www.sound101.org/index.php
"Fingernails scraping down a blackboard... the scream of a baby... your neighbour's dog barking: what is the worst sound in the world? This is what this website is trying to find out".
You can listen and vote on a collection of awful sounds, use the horrible sound mixer and even download horrible sound effects as ringtones.
The research is being done by Salford University’s Acoustic Research Centre and there's even scientific explanations about horrible sounds
Obviosuly this site has not yet heard the winner of last year's Worst Demo Ever Contest - Darwin's Disco Bagpipes!