The squeak of a marker on paper.
An eraser on a chalk board.
Someone brushing their teeth (other than me).
Someone gagging (including me).
Snorting (the sucking-a-loogie-into-your-throat snort, not a laugh snort, which I find charming).
Someone chewing gum with her/his mouth open.
Cats (LOL or otherwise).
Ann Coulter's voice.