AdAge [1] reports that Belgian ad agency Duval Guillaume is launching a new breath freshener with one one-second ads. See the one second ad here [2].

The breathmints name is "One Second", and the tiny ad is a basic product demonstration, a woman plops the gel-mint on her tongue, followed by a product shot as the product name is being whispered: "One Second".

"Since One Second is a small company with big ambitions, DGA had to think of a way to create rumor around the new product without it costing a lot," said Katia Strauwen, an account director at the agency. "So we decided to make the fastest, shortest commercial ever."

Except it isn't the fastest or shortest ad ever or even by a long shot. You knew I'd say that right? ;)
Back in 1993 the Guniess book of Records aired the world shortest ad, which was one second. These days, if you want to get into the Guniess book of Records you need to beat the more recent record holder Tharanga Ramanayake who created a campaign with 12 different versions of ads for MuchMusic, all only 1/60 of a second, or half a frame long that aired in 2002. The previous record holder was a feature film in comparison, it was 4 frames long and aired on KING-TV's Evening Magazine (USA) on November 29, 1993 and advertised Bon Marche's Frango sweets.

Guniess book of Records - worlds shortest ad - (1993) 0:01 (USA) [3]

Edit: Spotted that Adrants [4] wrote about this on friday, "Marketer Launches One Second Commercial" sans extra trivia on really short adverts.