The 50 people who matter today: 21-30

21-30 on our diverse list of individuals, couples and families changing the world, for good and ill.

21.Jimmy Wales

The Wiki man

Wales set up the biggest encyclopaedia ever compiled and revolutionised the way content is generated on the internet. His website Wikipedia established one of the first successful examples of "user-generated content" on the web, allowing visitors to the site to submit and edit articles. Wikipedia has more than ten million articles and reported 7.5 million unique users in August this year. Last year, Wales was called to meet with China's State Council Information Office to open dialogue on censorship. Unlike the internet heavies at Google, he has refused to submit a censored version of his site to China and continues to champion the model of collaborative, uncensored web publishing.

22. Amartya Sen

Nobel economist and thinker

If intellectuals "matter" insofar as they influence politicians and policymakers, then the Nobel Prize-winning economist Amartya Sen certainly does. When Nicolas Sarkozy declared recently that quality of life matters as much as GDP, he was channelling Sen. And when Brit­ish politicians argue that inequalities of "capability" matter as much as inequalities of income and wealth, they are rehashing one of Sen's most influential academic papers. His workhas also been vindicated by recent events: long before the crash of 2008 made the case for proper regulation of the financial sector irresistible, Sen was arguing that market economies are not free-standing, self-correcting mechanisms.

23. Viktor Bout

Lord of war

A former military officer, 42-year-old Viktor Bout built up a fleet of aircraft after the collapse of the Soviet Union and went on to become the world's largest arms smuggler, supplying some of the most unsavoury groups and regimes on the planet, including Colombia's Farc rebels, the former Liberian dictator Charles Taylor and Libya's Colonel Gaddafi. Or so say his opponents, notably the US, which has been trying to extradite him from Thailand for over a year. Some of his assets have been frozen, Interpol has issued a warrant for his arrest, and he has been the subject of UN sanctions. But according to his website he is just a "normal businessman striving for success".

24: Ashfaq Kayani

Pakistan's fighting chance

The government has repeatedly claimed that three in every four terror plots here in the UK have links back to al-Qaeda in Pakistan - where General Ashfaq Kayani, head of the Pakistan army, is the man responsible for the battle against the jihadists. He is also leading the fight against the Taliban along the country's border with Afghanistan, managing ongoing tensions with neighbouring India, and is in charge of securing his country's arsenal of roughly 90 nuclear warheads. To say his is a big job is an understatement of epic proportions.

In a country blighted by military dictatorships, where stability is threatened by Islamist militants, Kayani and his troops remain the dominant power. So far, however, he has stopped the army from meddling in politics. It was Kayani who ordered military officers to withdraw from their lucrative posts in civilian ministries and who kept his soldiers out of sight during the February 2008 elections. And it was Kayani who allowed the opposition to move against the then president, Pervez Musharraf, letting it be known there would be no military action to defend him.

A former chief of the notorious Inter-Services Intelligence agency, Kayani has been instrumental in brokering various deals that have dominated Pakistani politics. He is close to all major players - a confidant of Musharraf, the Bhutto family and the Pentagon. A quiet man, he tends to avoid the limelight. But given how many army chiefs have become president, he may not keep a low profile for long.
Mehdi Hasan

25. Warren Buffett

The philanthrope

With an estimated net worth of $62bn (£38bn), Warren Buffett - one of the most successful investors in history - regularly takes the top slot on the Forbes rich list. The "Oracle of Omaha" warned in 2003 that credit derivatives were "financial weapons of mass destruction"; his exceptional financial insight has led to his being touted as a possible future treasury secretary by Barack Obama, whose campaign he backed. He has invested hundreds of millions in eco-initiatives, and pledged to give away 85 per cent of his fortune to philanthropic causes.

26.Pope Benedict XVI

Papa Ratzi

The former Cardinal Ratzinger has always been a stern guard of Catholic doctrine: he ran what used to be the Holy Office of the Inquisition for more than 20 years and led the campaign against "liberation theology". But, as Pope Bene­dict XVI, he has gone even further. He reintroduced the Latin Tridentine Mass and lifted the excommunication on members of a renegade sect that includes a "bishop" who denies the Holocaust - suggesting to some that the liberal reforms of the Second Vatican Council were in danger of being reversed. He may lack his predecessor's charisma, but Benedict XVI still claims the allegiance of the world's more than a billion Catholics - one-sixth of the global population.

27. Jairam Ramesh

Green giant

Western diplomats credit Ramesh, India's new environment minister, with "getting" the scale of the climate change crisis, and - having been a long-time adviser to the Congress leader, Sonia Gandhi (no 31) - as key to India's crucial role in sealing a deal at December's COP15 summit. A former television anchor, he occasionally writes for the Times of India.

28. Ingvar Kamprad

Leader of the flat-pack

Why does Ingvar Kamprad matter? Well, the chances are that you're sitting on the evidence. Or lying on it, drinking from it, or storing your kitchen utensils in it. Kamprad is the 83-year-old founder of Ikea, the home furnishings giant that has come to dominate the way our homes and offices look. His "flat-pack" approach to furniture sales is integral to 21st-century capitalism: a system that promises choice and simplicity but where, in the end, the individual does all the work and the large multinational corporations pocket the cash.

29. Gordon Brown

Recession proof

He is insulted by Tories, battered by events and undermined in his own party. But on the international stage Gordon Brown has been credited with preventing recession turning to depression, and leading the economic fightback with his dramatic "fiscal stimulus" and bank bailout programmes. The Nobel Prize-winner Paul Krugman concluded that Brown, along with Alistair Darling, had "defined the character of the worldwide rescue effort". Although Britain's influence in the world is a fraction of what it once was, Brown's continued troop ­deployment in Afghanistan retains influence with Washington, and the UK still has the fifth-largest economy in the world.

30. Amr Khaled

Head preacher

Amr Khaled commands a larger television audience than Oprah Winfrey. His shows, broadcast on a Saudi-owned TV station throughout the Middle East, tell simple, often emotional stories about Islam. Their message is peaceful and uplifting - but also deeply conservative. Khaled is considered as responsible for large numbers of Egyptian women choosing to wear the hijab; and despite his fervent condemnation of Osama Bin Laden, not all are convinced that his influence is benign.