WASHINGTON, D.C. - Bill and Melinda Gates were among the many people honored Tuesday at the White House as recipients of the Presidential Medal of Freedom.

In his last Presidential Medal of Freedom ceremony at the White House Tuesday afternoon, President Obama feted one of the most high-profile groups in his eight years in the Oval Office: among them were the Gates, Bruce Springsteen, Tom Hanks, Robert DeNiro, Ellen DeGeneres and Michael Jordan. The nation's highest civilian honor was bestowed on a 21 individuals from a varying list of categories, from science to sports to entertainment.

"Today we celebrate extraordinary Americans who have lifted our spirits and pushed us to progress," Obama said in his introduction. "This is particularly impressive class: Innovators and artists, public servants and rabble-rousers, athletes and renowned character actors like the guy from Space Jam," jokingly referring to Jordan's 1996 animated basketball comedy.

The Gates were honored for the contributions of the Bill & Melinda Gates Foundation, which they launched in 2000 to help people lead healthier lives in developing countries and the U.S. According to the White House release, the Gates Foundation has donated $36 billion in grants.

“We are deeply humbled to receive the Presidential Medal of Freedom for our foundation’s efforts to make the world more equal for everyone. Humanity’s greatest advances are not in its discoveries – but in how those discoveries are used to reduce inequity. We rely on our dedicated staff and thousands of innovative partners across the globe to help end poverty, hunger and disease, as well as improve U.S. education. Their dedication and talent make us optimistic about the future, and we accept the Presidential Medal of Freedom in their honor and on their behalf," Bill and Melinda Gates said in a released statement.

Obama praised the Gates' for their work in the medical, education, and environmental fields.

"Many years ago, Melinda's mom told her an old saying: "To know that even one life has breathed easier because you lived -- that is success." By this and just about any other measure, few in human history have been more successful than these two impatient optimists," Obama said.

During the ceremony, Obama called out De Niro as a sensitive artist who could blend dramatic precision with comic detail: "His characters are iconic: a Sicilian father turned New York mobster, a mobster who runs a casino, a mobster who needs therapy, a suburban father whose scarier than a mobster, Al Capone."

Poking fun at Hanks' movies, from Cast Away to the recent Sully, Obama said that something always happens to him on screen "and yet somehow we can’t resist going where he wants to take us. ... He has introduced us to America’s unassuming heroes." Yet he also paid tribute to how Hanks — whom Obama called "America’s dad" — stood up to cancer with wife Rita Wilson. "The truth is Tom has always saved his best roles for real life. He is a good man."

The president became a little choked up when recalling how DeGeneres came out as gay on an episode of her TV show Ellen in 1997, a move not only important to the LGBT community but one that could "challenge our own assumptions," Obama said. "What an incredible burden to bear, to risk your career like that. ... And yet today, every day and in every way, Ellen counters what often divides us and inspires us to be better, one joke and one dance at a time."

Hollywood legend and activist Robert Redford was hailed by Obama for applying "his talent and charm to achieve success," while he reminded the crowd of how Saturday Night Live's Lorne Michaels created a late-night comedy show that was "a mainline not just into our counterculture but our culture. It's still a challenge to the powerful, even folks like me."

Other honorees included actress Cicely Tyson, architect Frank Gehry, NASA computer scientist Margaret H. Hamilton, Vietnam Veterans Memorial designer Maya Lin, Elouise Cobell, a Blackfeet Tribal community leader, and Richard Garwin, a polymath physicist.

"This is America," Obama said in regards to the new medal recipients. "It’s useful when you think about this incredible collection of people that this is what makes us the greatest nation on Earth — not because of our differences but because in our difference we find something common to share."