Ryanair [1] - misleading and unfair comparisons
Special K [2] - misleading health claims
Hooters [3] - too objectifying
Unforgivable [4] - this one gets "banned" with BS-quoties around it.
Links:
[1] http://www.theregister.co.uk/2007/10/18/ryanair_advert_banned/
[2] http://media.guardian.co.uk/advertising/story/0,,2192492,00.html
[3] http://www.wptz.com/news/14348916/detail.html
[4] http://www.eurweb.com/story/eur36838.cfm
[5] http://technorati.com/tag/advertising news