The most controversial—and effective—ads ever?

Benetton | Fabrica, 72andSunny

Advertising has long been recognized – and criticized -- as an efficient way to persuade us to spend our money. But sometimes the "Mad Men" have chosen to take a risk, go beyond the "soft sell", and seek to challenge the way we think.

They have flirted with race, religion, sexual orientation and more to make people question their belief systems – and boost their brand at the same time.

"The cleverest thing an advertiser can do is the opposite of what everyone else is doing," said Daniel Hennessy, U.K. chief creative officer at Geometry Global agency, who compiled this list of controversial ads for CNBC. "Sometimes it's risky, yes; but it's better to be talked about than not talked about."

Click ahead to see some ads from around the world which aimed to change the way that people think.

- By CNBC's Katrina Bishop @KatrinaBishop

Westinghouse Electric - We Can Do It!

Santa Fe College | Westinghouse Electric

When: 1943

Creator: J. Howard Miller

Why it matters: Now considered an icon of World War II, "Rosie the Riveter" is often mistakenly assumed to be part of a U.S. government program to encourage women into the workplace during wartime. Geometry Global's Hennessy said the image remains "one of the earlier depictions of empowered women".

In fact, the poster was commissioned to improve productivity of employees already working at Westinghouse Electric and Manufacturing Company.

Tülin Erdem, professor of business and marketing at the New York University's Stern School of Business, said Rosie was an example of how campaigns' meanings can get distorted over time.

"It's taken on a life of its own," she told CNBC. "Today, nobody remembers that it's about a company wanting its employees to work harder."

Henry S. Levy and Sons - You don't have to be Jewish

University of Michigan | Henry S. Levy and Sons

When: 1961

Creator: Doyle Dane Bernbach (DDB)

Why it matters: Showing non-Jewish New Yorkers eating a sandwich made from the baker's rye bread, together with the tagline: "You don't have to be Jewish to love Levy's", this ad broke new ground in using positive religious references in advertising.

"What we wanted to do was enlarge its public acceptance. Since New York is so mixed ethnically, we decided to spread the good word that way," Judy Protas, copywriter at DDB, told The New York Times in 1979.

"This was very different for its time, and using religion is risky," Ann Green, senior partner at Millward Brown brand consultancy, told CNBC. "This use of religion, though, was effective because the product, bread, is nearly universal and it engaged all religions in a clever, light-hearted way."

The Health Education Council - Pregnant Man

Family Planning Association | Cramersaatchi (Saatchi & Saatchi)

When: 1970

Creator: CramerSaatchi, now Saatchi & Saatchi

Why it matters: This British campaign to promote contraception was so successful that the agency behind it named its in-house pub after it.

"This was one of the first examples of an ad flipping cultural norms," Geometry Global's Hennessy told CNBC. "It might seem a bit old hat now, but at the time it was very impactful."

Erdem highlighted that the ad was "educational, without being moralistic or patronizing."

In the book "Saatchi & Saatchi: The Inside Story", John Hegarty, who worked on the campaign, is quoted as saying: "The Pregnant Man was more than just a piece of advertising; it was the first time I had seen a piece of work that moved beyond the accepted boundaries our business operated in, commanding attention from a far wider group of people."

Lynx - Dumb Animals

Lynx (Respect for Animals)

When: 1983

Creator: Yellowhammer, David Bailey

Why it matters: British anti-fur pressure group Lynx – now Respect for Animals – ran this campaign throughout the 1980s. It is credited with changing British attitudes to fur – eventually leading to the closure of stores' fur departments and bringing an end to the country's fur farming industry.

"Lynx is saying if you wear fur you are dumb. Who wants to be dumb? Not me… Pretty much not anyone! Shame is a very strong emotion," said Millward Brown's Green.

Celebrity-photographer David Bailey oversaw the creative sign of the campaign, working for free.

"What's particularly interesting is that this ad isn't targeting the women who are wearing the furs; it's targeting other people to put pressure on people who wear furs," Professor Erdem added. "In this case, it's OK to be moralistic, because the ad isn't judging its target market."

Dove - Real Beauty Campaign


When: 2004

Creator: Ogilvy & Mather and others

Why it matters: When this campaign was launched in 2004, some 75 percent of women felt that advertising and media set unrealistic standards of beauty, according to Dove.

"The central goal of Dove's Real Beauty campaign is to make beauty a source of confidence, not anxiety for women everywhere," said Lucy Attley, Dove's brand director, in a statement to CNBC.

The ongoing global campaign aims to boost women's confidence by focusing on the beauty of "real women".

Professor Erdem named the award-winning Real Beauty Sketches – in which a forensic artist draws women based only their own description of themselves – as a highlight of the campaign.

"Women – the target audience - reacted in a very emotional way to this ad," she said. "Even the parodies (when men described themselves) reinforced Dove's message."

Obama Presidential Campaign - Hope

Nicholas Kamm | AFP | Getty Images

When: 2008

Creator: Shepard Fairey

Why it matters: The "Hope" poster has become an icon of now-U.S. President Barack Obama's 2008 presidential campaign.

Interestingly, though, the poster was not commissioned by the campaign, and was only used by Obama's team following initial success after its production – independently - by artist Fairey.

"It became very clear quickly that the demand for an image like that had not been supplied and that the Obama supporters were very hungry for it and also very motivated to spread it," Fairey said in an interview with The Huffington Post in 2008.

For Millward Brown's Green, the Obama campaign's adoption of the ad wasn't risk-free. "This approach was unexpected – it really touch(ed) voters emotionally in a category often full of negative or attack ads," she said.

Benetton - Unhate

Benetton | Fabrica, 72andSunny

When: 2011

Creator: Fabrica, 72andSunny

Why it matters: United Colors of Benetton has long been known for its controversial ads, and its Unhate campaign was no different.

The manipulated images showed world leaders kissing, including Obama smooching with then-China President Hu Jintao, and Palestinian President Mahmoud Abbas getting up close and personal with Isreal Prime Minister Benjamin Netanyahu.

The company said the ads had the aim of "contrasting the culture of hatred and promoting closeness between peoples, faiths, cultures, and the peaceful understanding of each other's motivations".

Geometry Global's Hennessy said Benetton had always set out to shock, but this time he wasn't sure the campaign had managed it.

"It's become quite hard to shock us now, but this does raise points of cultural difference, security and conflict – all in one picture," he said. "It's part of the brand's history. They're not using advertising to push their product, but everyone will talk about this. And no one talks about a Gap ad."

Channel 4 Paralympics - Meet the Superhumans

Channel 4, 4Creative

When: 2012

Creator: 4Creative

Why it matters: "London 2012 is a coming-of-age moment for the Paralympics. This campaign will help bring a whole new audience to it and may even raise a goosebump or two along the way," Dan Brooke, Channel 4's chief marketing and communications officer, said at the launch of this ad.

It won big at the global Association for Creative Advertising and Design's (D&AD) annual awards, where it was described as presenting the "Paralympians as powerful warriors rather than people to pity".

Millward Brown's Green's said this ad was her favorite in this list. "It hits on the emotional front. And while classic, it is done in a very fresh way," she added.

King Khalid Foundation - Can't Be Covered

King Khalid Foundation | Memac Ogilvy Riyadh

When: 2013

Creator: Memac Ogilvy Riyadh

Why it matters: In April 2013, the King Khalid Foundation launched Saudi Arabia's first ever campaign against domestic abuse, aiming to generate awareness of a subject long considered taboo in the state.

"We initiated a proactive campaign that was both controversial, but also paid homage to the culture that exists in Saudi Arabia," the agency said on its website. "A campaign that could only have come from the Kingdom, was a first and heralded as ground-breaking."

Millward Brown's Ann Green said the images are powerful in their simplicity, and "also quite unexpected."

"As the first campaign of its kind to run in Saudi Arabia, it doesn't waste any time in literally looking you straight in the eye, pulling at your emotions and asking for your help," she added.

In the summer of 2013, Saudi Arabia passed a new law to criminalize domestic abuse.

UN Women - The Autocomplete Truth

UN Women | Memac Ogilvy & Mather Dubai

When: 2013

Creator: Memac Ogilvy & Mather Dubai

Why it matters: Seeking to raise awareness of sexism and discrimination against women across the world, the ads show the autocomplete search options that appear when "women shouldn't" and similar phrases are typed into Google.

The agency said the campaign "held up a mirror to the world and exposed the hidden truth on gender bias that still prevails today".

The ad was named the "most shared ad of 2013" by Adweek, and "Social Good Campaign of 2013" by the Ad Council.

"This ad speaks for itself. When you see what comes up in the autocomplete it's appalling," said Geometry Global's Hennessy. "They've piggybacked on something that's actually happening in culture and used it to highlight their message."