The world of Avatar: The Last Airbender is filled with talented people, and within Team Avatar, each group member brings something special and unique to the table. Some of the skills they bring are obvious, such as their main forms of bending or Sokka's boomerang expertise, but others are a bit more discreet. These talents will also include those of latter Team Avatar members, such as Suki and Mai, but their abilities are still just as valuable and interesting as the rest.
Of course, these hidden talents also range in usefulness, with some having more of a performance value over anything else such as Sokka's "special knot." But even though some have the edge over the others, they all still contribute to the dimensionality of the characters, and each talent is intrinsic to the team as a whole.
Mai's Athleticism
Mai is about as gloomy and aloof as can be, but in the episode "The Beach," she shared an uncharacteristically angry and vulnerable side and even showcased some moves that no one saw coming: her incredible volleyball talent.
Though all four of the Fire Nation teenagers were pretty good, her abilities are the most surprising, as her character is someone who wouldn't likely put the time or effort into learning the necessary techniques or rules of the game. But all things considered, it was a good move by the writers, as it gave her persona a little more depth than just the usual doom and gloom.
Suki's Animal Whispering
Suki has an amazing sense of style, combat technique, and acrobatic talent, but her ability to communicate with Appa in "Appa's Lost Days" really pushes her character to the top as a fan-favorite in the series. In the episode, Suki is the only person able to get through to Appa after his ordeal at the circus, and it's truly a heartwarming and beautiful moment.
What's interesting is that in "The Serpent's Pass," after Sokka begs her to reason with the creature, Suki tells him, "Just because I live near the Unagi doesn't mean I'm an expert!" She clearly shouldn't have sold herself short, as her Appa-whispering showcased, so maybe Sokka's idea would have worked if she'd just deployed some of her impressive talents.
Iroh's Musical Abilities
Iroh is shown to be proficient in the tsungi horn throughout the series, playing eloquently in both "The Blue Spirit" and his tea shop in the final scene of "Sozin's Comet." His famous ballad, "Little Soldier Boy," is played on the pipa, a string instrument, and these probably only scratch the surface of his musical expertise.
As such a gentle, loving character - as shown through some of Iroh's best quotes in ATLA - it makes perfect sense that he is the musician of the group, and his song, "Little Soldier Boy," is one of the only ways he ever exhibits his pain over the loss of his son, Lu Ten. Iroh's music adds a level of vulnerability to his character, allowing him to step out of his tireless mentor position and just be human for once.
Appa's Hearing
Appa comes to rescue Aang and his friends many, many times. He saves them from angry pirates in "The Waterbending Scroll," as well as an even angrier Azula in "Return to Omashu," and it's all because of his very acute sense of hearing. He is able to hear Aang's bison whistle from miles and miles away, and the skill often goes as one of Appa's less appreciated abilities compared to his airbending and flight.
Even so, it certainly came in handy during the series, and the group would have perished had Appa not shown this capacity all those times.
Momo's Endurance
The flying lemur displays a lot of skills during the run of the show, such as his dexterity and intelligence shown in "The Tales of Ba Sing Se," but he also has a much bigger and less discussed strength. That is, his ability to survive and endure. After the team finds him in "The Southern Air Temple," Aang looks at him and says, "We're all that's left of this place."
With that logic, Momo must have been alone for years in the skeletal, hostile environment of the abandoned temple. His chattering and intelligence prove that he's an incredibly social creature, so it's really a wonder how he managed to survive all that time.
Toph's Lie Detection
This one falls more on the "not-so-hidden" side of things, as Toph's ability to detect lies is a major plot point in several episodes and provides some of Toph's best moments in ATLA. It helps the gang discover that Jet was brainwashed in "Lake Laogai," and in "Day of Black Sun," Azula tells a blatant lie to Toph in order to prove her deceptive abilities, to which Toph is forced to concede, "Okay, you're good, I admit it."
However, in normal cases, Toph can usually tell if anyone is lying by feeling the vibrations of their heartbeat with her earthbending abilities. It's a rare and incredibly useful skill, and she was the first one in the Avatar universe to ever pioneer bending as a form of lie detection.
Sokka's Artistic Side
Sokka's character arc is one of the best in the original series, and his transformation from a silly teenager to a fully capable warrior is certainly one to behold. He gains an amazing tactile sense and swordsmanship ability by the end of The Last Airbender, but his final scene with the ink drawing proved he was still the same Sokka (with the same artistic tendencies), though to call them a hidden "talent" is perhaps a stretch.
In "The Library," he presents his special knot to the owl and is scoffed at, and in "Sokka's Master," he receives a similar response from Piandao when he adds a rainbow to his painting. However, this artsy side is what established Sokka as such a smart and unique warrior, and it often enabled him to think outside the box when the team found themselves in sticky situations.
Zuko's Motor Skills
Zuko has a lot of incredible abilities, including hand-to-hand combat, swordsmanship, and firebending, but some of the least discussed are the motor skills he exhibits throughout the series. In "The Siege of the North," he holds his breath for a seemingly impossible amount of time, and in "The Waterbending Master," Zuko somehow manages to hear the tiniest creak from the pirates tiptoeing the ship deck.
Zuko shouldn't have been able to survive for so long in the icy water of the North Pole, and he should not have lived through the pirate's assassination attempt, yet he did. Perhaps it's just a manifestation of his unbreakable spirit. Either way, these characteristics add to Zuko's mystique, and they are a large contributor to his survival in all of these harrowing situations.
Aang's Jewelry
After Katara loses her necklace in "Imprisoned," Aang creates an intricately knotted replacement for her out of fishing line in "The Fortuneteller." When Sokka tells him that he should go into the jewelry-making business instead of saving the world, Aang says, "I don't see why I can't do both!"
This talent helps round out the softer, pacifist side of Aang, and it's a nice contrast to his martial art prowess. The necklace is also an indication of how much the air nomad's peaceful core contradicts the violence necessary to be an Avatar, and it's a nice setup for the upcoming tensions between Aang's destiny to defeat the Fire Lord and his inner jewelry-making
Katara's Dancing
As a natural athlete and acrobat, it makes sense that Aang would excel as a dancer, but Katara's abilities come a little more out of the blue during the kids' dance party in "The Headband." With one small whisper from Aang, the two begin the dance, and they somehow pull off some amazing choreography
Katara's history never indicated this level of dancing expertise, but it adds a little more dimensionality to her character, allowing her to step out of the "mom" position of the team and just be a kid like everyone else. And, of course, it's a cute talent to bond over with Aang.