The TUI advert with the girl who has the whole hotel and seemingly entire universe revolve around her while her boyfriend lurks in the shadows/off camera like some sort of afterthought. Can't stand that advert.
The Nationwide ones, as many others have said, incredibly annoying. Someone needs to tell the blonde woman the strange egg timer/shaker isn't a musical instrument in the same league as a piano.
Also, the advert for Oral B with the Arnie style dentist, "my gums are sore, but no need to worry, right..?" " WRONG!")