This thread is the reason I prefer radio to TV.
My hated faces are:
Daniel Radcliffe, Rupert Grint, Emma Watson. Daniel because he has the same wooden expression throughout all eight of the films, and the other two because their expressions were always wildly exaggerated. Also when the first film was out, life-size cardboard cutouts of the trio were everywhere. I thought Hagrid was rather unpleasant to look at as well.
In fact, I loathe any face which is massively blown up to fit on those huge adverts that appear beside roads. Some others have been:
Mr Bean's holiday - ugh. I'm surprised nobody has said Rowan Atkinson so far, whose face is one of his main tools. Baldrick was right when he said "you rubber-faced bastard". But I agree with @alltoomuchrightnow about Tony Robinson - in "Baldrick's video diary", he's constantly looking into the camera: shudder.
David Cameron, with that poster "I'll cut the deficit, not the NHS".
A bloodied face which said "advertise with impact".
When camera phones were new, a huge close-up of a child's face with the mouth covered in toothpaste.
The cover of the Radio Times used to show the worst of faces (I don't know if it still does): frequently some celeb with eyes and mouth wide open, sometimes with a plastic red nose. My mum used to ceremonially destroy the covers of any Radio Times which had an ugly grinning face on the front, saying "I do not understand why they put so much value on the human face". She used to do the same with cereal packets that had grinning faces, such as the Frosties tiger (and she disapproved of Frosties as well).