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Justin Timberlake and Taylor Swift walked away with a ton of awards on Sunday night, but five killer collaborations stole the show at the 2013 American Music Awards in Los Angeles. From Christina Aguilera lending her powerhouse pipes to a duet with an up-and-coming duo to Lady Gaga's presidential duet with R. Kelly, here were the five freshest moments from the 2013 AMAs.

5. Christina Aguilera/A Great Big World

As a coach on The Voice, it's no secret Christina Aguilera has an ear for talent. So even if you hadn't heard of indie duo A Great Big World before the AMAs, you shouldn't have been surprised how flawless their "Say Something" duet with Xtina was. It was a heartfelt moment of unadorned, expertly-executed vocal power.

4. Pitbull/Ke$ha

Pitbull pulled double duty at the 2013 AMAs. He not only hosted the three-hour awards show at L.A.'s Nokia Theatre but also performed "Timber" with Ke$ha for the first time on live TV. Melding hip hop, blues and dance-pop, "Timber" proves that three great (but wildly different tastes) can combine to create a crazy-fresh flavor with an unexpected punch. Oh, and Ke$ha's glitzed-out Daisy Dukes? So hot.

3. TLC/Lil Mama

Two decades after being nominated for their first American Music Award, TLC returned to the AMA stage and sang their all-time classic "Waterfalls." Although Lisa "Left Eye" Lopes can never be replaced, Lil Mama—the Brooklyn rapper who played the late singer in the recent TLC biopic—filled in for TLC's fallen sister by spitting a hard verse. It was a beautiful, bad-ass and bittersweet moment at the AMAs.

2. Florida Georgia Line/Nelly

The craziest collabo of the night was Florida Georgia Line and Nelly. No, it wasn't shocking they performed their smash "Cruise" together (which won Single of the Year later that night). But it was a surprise when the country duo backed up Nelly on his 2001 megahit "Ride Wit Me." The Southern twosome demonstrated their versatility by joining the St. Louis MC on the chorus and even rapping a little on the verses, proving that these two country boys can spit a rhyme when push comes to shove.

1. Lady Gaga/R. Kelly

Lady Gaga and R. Kelly owned the night with a duet that melded her dance theatrics with his off-kilter comedic genius. Seated in the Oval Office, Kellz was cast as the President of the United States while Gaga played his Marilyn Monroe-esque mistress, grinding with him and shaking her glittery tassels under his executive orders. Seeing them perform together is a reminder that even if you think you've tasted it all, inventive artists like these two can still dazzle us with their unique vision.

All in all, the 2013 American Music Awards proved that the best things happen when unexpected flavors combine to make something entirely fresh and new.