Tali'Zorah nar Rayya is a companion from the Mass Effect Trilogy. She's from an alien race called the Quarians, who wear protective enviro-suits because their bodies have weak immune systems; they lived for generations on a homeworld with few diseases and then on space ships with sterile environments. Thus, Tali is easily recognized by her purple suit.
When Shepard meets her in the first game, Tali is a young woman on her species' coming-of-age ritual, the "Pilgrimage." By the end, she is a competent fighter and an avid ally to the player. Tali is widely recognized as one of Mass Effect's best companions. These reasons justify why she's at the top of that list.
10 Mechanical Genius
Quarians tend to be good with technology since their entire species lives on a fleet of ships in space. They need to, at least, be able to maintain their enviro-suits, which protect them from getting sick. Tali is the extreme of her species — a mechanical wunderkind. In the game, she's labelled under the category of "Engineer," which is basically Bioware's science-fiction response to rogues. She takes a particular interest in the Geth, a sentient race of robots that were created by the Quarians long ago.
9 Her Struggle With The Geth
Across the trilogy, Tali takes a special interest in the Geth. During her Pilgrimage, before meeting Shepard, her curiosity about the Geth led her to discover information about Saren. The Quarians have been at war with the sentient robots for years, and Tali struggles to balance her empathy with her anger. Watching her do so, whatever side the player picks by the time of Mass Effect 3, is character development at its finest. And, if they do choose just the right things to do and say, Tali's knowledge turns to anger turns to understanding, and the result is beautiful.
8 She's In Every Game
Tali stands by Shepard's side as a companion through every Mass Effect title. Though some companions from the first Mass Effect make surprise appearances for special missions or brief chats, Tali is actually a recruitable teammate in every game.
The only other companion that shares this status with her is Garrus, the Turian sniper. Her loyalty to Shepard comes from a passion for their cause and a love of travelling the world; once Shepard died between Mass Effect and Mass Effect 2, she became a respected figure among her people and began leading missions herself.
7 Her Romance
Tali's romance is beloved by many fans, for good reason. A witty, intelligent woman, Tali is more than a match for any Commander that the player decides to roleplay. When the pair first strike up a relationship, though, Tali is nervous — she's used to being treated as less-than by most humans, who see Quarians as inferior due to their weak immune system. But, if Shepard reassures her and continues to flirt, they eventually strike up a caring relationship. Admittedly, her enviro-suit makes things complicated, but Mordin (the ship's doctor) is more than happy to offer Shepard advice about self-sterilization and Quarian physiology.
6 Her Combat Drone, Chatika
BioWare is a developer that loves to fill their games with mischief and nonsense, and Tali's Combat Drone, Chatika vas Paus, is among the best. Any engineer in Mass Effect can summon a combat drone to fight with them, but Tali names hers and has a special connection to it.
Chatika's name is a secret reference to BioWare's Baldur's Gate II, in which "Chiktikka Fastpaws" is a raccoon companion to a party member. If the player is listening closely, they can hear Tali shouting things at Chatika that are further references to Baldur's Gate.
5 She Takes Your Name
Quarians have slightly unusual naming conventions (at least, by human standards). They are composed of four parts: the Quarian's birth name; the Quarian's family/clan name; their title; and the name of their ship. When Shepard first meets Tali, she is called Tali'Zorah nar Rayya (literally: Tali Zorah, child of the ship Rayya), and when she appears again in Mass Effect 2, she is called Tali'Zorah vas Neema (literally: Tali Zorah, crew of the ship Neema). However, if Shepard finishes her loyalty quest during Mass Effect 2, she proudly decides to become Tali'Zorah vas Normandy. Tali takes that name into the rest of the series, as a constant reminder of who her chosen family is.
4 She's A Hilarious Drunk
It's not clear if being a Quarian makes her a lightweight, but Tali sure does get drunk a lot in Mass Effect. On multiple occasions, Shepard will find her drinking away her frustrations after missions or during parties. After the mission to Horizon in Mass Effect 3, when Shepard comes face to face with Miranda's father, Henry Lawson, Tali is particularly upset. She gets drunk on Turian brandy (supposedly it's strong stuff) and reflects on how she's treated Miranda. Or, at the Commander's party during Mass Effect: Citadel, she can be found on the bathroom floor after drinking all night, murmuring things like "Go for the optics, Chatika..."
3 She's Close To Garrus
Tali and Garrus are the only companions of Shepard's that are with him throughout every game. As a result, they form a special bond with one another. No one else has seen the whole saga as they have. They can be spotted visiting the other's location on the Normandy every once in a while.
In fact, if the player doesn't choose to romance either of them, they start a relationship with one another towards the end of Mass Effect 3. Though Tali tends to deflect with humor, joking that it's just a "fling," Garrus admits that it's nice to have someone to come home to, to fight for.
2 Watching Her Grow Up
One of the best parts of Mass Effect is watching Tali grow up from a young woman, fresh off the boat, too idealistic and trusting for her own good, to a self-confident leader of her people, willing to fight — and hard — for what she believes in. Each game comes with a new challenge for Tali to overcome, whether it's completing her pilgrimage, standing up for herself in court, or learning to accept Legion as a companion. By the end, Tali'Zorah is a completely reimagined woman in a world teeming with possibilities for her.
1 Her Role In Quarian Politics
Tali's influence on the future of her species is exhibited time and again throughout Mass Effect 2 and 3. In the second game, she must defend herself against accusations of treason by her people. In the third, she struggles with her people in the war against the Geth. Though her background is hardly in political science, Tali knows what is right and fights for it — even if she needs an occasional nudge in the right direction from Shepard. The Quarians have been adrift in space on their ships for generations; they are desperate for a new path, and Tali has one.