Austin of Austin & Ally: Even if he screws up sometimes, he is nice to a fault. He's sweet, gentle and when he comes to understanding the feelings of others if he has hurt them, he will try his hardest to make up for it. Go look at the Heartwarming page for examples.
It has Dr. Rich. A Nice Guy who can't hold a grudge. He volunteers once a month in Central America to fix cleft palates, cleans up rivers, and teaches seeing-eye dogs. In his free time he makes kettle corn and takes pottery classes to unwind from the pressures of his job, he hasn't lost a patient in five years. Oh, and he'll also show you how to check for breast lumps.
Season 3 gives us Todd, a loving father and retired Marine whom everyone hates.
In the main cast, Troy is the only one who's never been given any serious social flaws, and has never been cast in a villainous role.
Jimmy from early Degrassi: The Next Generation — he's almost like a medieval knight, in being both a perfect gentleman and somewhat clueless and stiff. He loses his girlfriend to a sensitive Emo Teen who understands emotions better, and his honor code means that he refuses to participate in gang bullying, but is utterly ineffective at stopping the bullying.
Rory Williams of Doctor Who. A nurse who became the Victorious Childhood Friend to the Doctor's companion, Amy Pond. Of course, his nice guy attitude allows him to act as an interesting foil for the Doctor. Besides, if you hurt his wife you better Beware the Nice Ones, because you've now got the 2,000 year old Last Centurion on your tail.
Ross is Adorkable and romantic. He becomes a good father to his son Ben and he manages to get on well with his ex-wife Carol.
Joey is incredibly loyal and a great friend. He manages to be a good guy despite his womanizing ways.
Chandler, despite his sarcastic defence is a total sweetie, constantly puts his friends and later girlfriend ahead of himself, and comes out with some of the most thoughtful moments in the series.
Phoebe's husband Mike is a sweet generic guy who loves Phoebe and enjoys taking care of her. He doesn't mind that his upper-class family frowns upon their relationship.
Phoebe's first serious love interest, David "the Scientist Guy". He's a cute geeky guy who is crazy about Phoebe and would do anything for her. Too bad his career takes him to Minsk and they are separated.
Ross and Monica's father Jack Geller is a good man who loves his family. His only fault is that he did not notice his wife Judy was emotionally abusive to Monica.
Monica's season 2 boyfriend Richard Burke is one of the nicest characters on the show. It's lampshaded by Chandler who tells him that he's a good guy. Richard replies that he hates that.
Game of Thrones: Renly Baratheon is the only man who has treated Brienne of Tarth with kindness and respect, and he's probably the only king who has accepted a woman into his Kingsguard. He does this despite knowing full well that it would shock his bannermen, annoy his wife, and piss off his lover. He himself understands how painful it is to be frequently mocked for not adhering to rigid gender roles (his older brothers Robert and Stannis have bullied him for his lack of combat experience), so his empathy towards Brienne's situation allows him to be accepting of her masculinity. Renly praises Brienne's martial skills and her devotion when his boyfriend Ser Loras Tyrell confronts him about it. Margaery Tyrell describes her husband as "brave and gentle" in "Dark Wings, Dark Words."
This is a notable deviation from the books.
Amidst the Loads and Loads of Characters on the show, you could count the number of openly genuine Nice Guys and Girls on one hand (that has several fingers missing). However, Ser Barriston Selmy and Davos Seaworth pass muster (the former an upstanding knight, the latter a moralistic smuggler), as does Brienne of Tarth, who can be surly at times, but adheres to a high code of honour.
Most of the Stark family, be it Ned, Robb, or Bran. Ned is shown to be greatly respected and admired by the smallfolk under his care, many of whom are still loyal to the Starks, long after most of them have been wiped out.
Jon Snow is definitely a Stark in all but name, widely considered one of the most compassionate and moral characters in the series. His best friend Sam Tarly also qualifies.
Ted, the protagonist. Although he has his Jerk Ass moments like the rest of the characters, he's almost ridiculously hospitable and helpful towards his friends (to the point of once selling his new car to loan Marshall money after the latter loses his job, giving Barney and Robin scads of relationship advice despite the latter being his ex-girlfriend, and giving Marshall and Lily his own apartment as a baby shower gift, complete with a handmade crib, when he realizes they are miserable in the suburbs). He's also a hopeless romantic and sentimental sap, which is frequently highlighted by the show's penchant for gender-flipping tropes. One of the foremost examples: to dissuade her from having sex, he regales Robin's teenage sister with a story about how back in high school, he said "I love you too" to his girlfriend after she said she loved him to get in her pants, ran off the moment he finished banging her, and never called her back. He says that all teenage boys are like this, even the 'nice' ones like him. However, Ted later confesses that the roles were reversed — he was in love with the girl, who lied about being in love with him back to make him put out and never called him back.
Ted's best friend Marshall is pretty much the poster-child for this trope. He's sweet, sensitive, innocent, good-natured, idealistic, romantic, and can't bear to hurt anyone (which is why it's such a shock when he beats a guy unconscious in retaliation for punching Ted). Also puts him into Gentle Giant territory given that Jason Segel is about 6'4.
Dangerous Davies from The Last Detective. If it wasn't based on a novel series and previously played 30 years ago in a one shot film by Bernard Cribbins, it wouldn't be farfetched to think that this role was created exclusively with Peter Davison in mind. D.C. Davies is called Dangerous because he's anything but. He's called the Last Detective because he's the last one anyone thinks of to send on an important case. He's honest, fair, non-assertive, and generous. These are the sort of things that apparently make a bad cop. This is true since all the other coppers are portrayed as cynical, hardened, insensitive, and borderline corrupt.
Miss Brooks is a nice girl example, who is always trying to help others (and marry Mr. Boynton). Mr. Boynton is also a nice guy, unfortunately for Miss Brooks, he's Oblivious to Love. Miss Brooks finally marries him in the Grand Finale.
Mrs. Davis, Miss Brooks' landlady, is a second nice girl example.
Harriet Conklin also counts as a nice girl example. Her father, scheming and domineering Principal Osgood Conklin, is definitely not a nice guy. Walter Denton may be nice overall, but is too much of a prank player and troublemaker.
Power Rangers. If you're going to be the Red Ranger, it's practically mandatory that you're one of these.
T.J.'s moment in Turbo came when he helped Bulk and Skull out of a predicament where they were being blamed for some packages disappearing, going on a stakeout with them and even helping set a trap for Divatox's minions when the Rangers found out she was behind the thefts. The whole time, T.J.'s just as concerned with clearing Bulk and Skull's names as he is with foiling the bad guys' plans.
Early on in Time Force, Wes's limo is struck by a stray baseball. Wes gets out and tosses the ball back to the child who threw it with a smile and without saying a word. He also buys contemporary clothes for the rest of Time Force and helps them get acclimated to the 21st century.
In an early episode of Power Rangers Megaforce, Troy doesn't hesitate to come to the aid of a younger student who's being bullied.
The "well-balanced" part doesn't apply (in fact, he has myriad issues), but otherwise Ned from Pushing Daisies fits this pretty well. He may be a bit aloof, but he's just shy, not rude, and he's sincere, kind and principled.
Quantum Leap: Sam Beckett. He's not quite an All-Loving Hero, but he's friendly, never takes advantage of women, and well, the fact of the matter is he always wants to help people he's around, even when they annoy him.
Kes of Star Trek: Voyager is possibly one of the nicest people in the whole franchise. She's sweet, understanding, kind but not spineless, advocating for the Doctor and wanting to learn as much as she could about the universe during her nine-year lifespan.
Sam is the perfect example of Nice Guy. This really piss him off because everyone keeps taking advantage of his nature. Then we discover his origins; he's a nice guy after that, despite his Dark and Troubled Past. He does have vague stalkerish tendencies and dates his employees.
Major Healey from I Dream of Jeannie is made of this trope. He treats Jeannie a lot better than Major Nelson does, and is always going out of his way to support and cheer on the other characters.
Most of the other characters are unfailingly polite and fit into this trope. The older male authority figures are stern but very polite and supportive (especially considering all the hijinks that the Majors and Jeannie pull, and are surprisingly forgiving and fair (if somewhat by-the-book). When the psychologist found out that Major Nelson was being investigated as a tax cheat, he was quick to defend him. And Major Nelson might be somewhat uptight and exasperated by all of Jeannie's stunts, but he clearly cares a lot about her, too, and will often go out of his way to do nice things for her and Major Healey.
While most people in Taxi are generally very kind, Reverend Jim Ignatowski stands out. Anyone that considers Louie not only as a friend, but a hero, is enough justification for him to fit in this trope. And that's just the beginning.
Zena Sherman, Louie's girlfriend qualifies by just being "Louie's girlfriend" regarding his personal problems. In spite of breaking up with him in the third season premiere, she wanted to be friends with Louie, though it's clear that he would never accept that.
Lister and Kryten from Red Dwarf both fit this trope, although Lister is quite good at standing up for himself against Rimmer or Cat, wheras Kryten has some programming to overcome in order to find a backbone.
Xander. A friend to pretty much everyone who is not a vampire, his Undying Loyalty is pretty much a superpower to someone who is just a Badass Normal in a World of Badass. Indeed he was The Heart to a spell to possess Buffy, and had this trait in the series as a whole, trying to reach out to any human person in their time of need, even Faith after she kills someone and shows no remorse for pinning the blame on Buffy.
Riley gets something of a Deconstruction early on - he was a prime example of how to not do this character since he ended up being regarded as a bland Replacement Scrappy for Angel (and later attempts to make him more compelling as a Love Interest for Buffy worked.). However, Riley comes back to the show Happily Married and his nice guy persona is much better executed. When he finds Buffy working in a dead-end job and sleeping with Spike, Riley refuses to condemn her for it, instead giving Buffy the encouragement to start pulling her life back together. His wife, Sam, is really really nice and supportive, even when Buffy kills a demon they were tracking.
A female example is Tara McClay, most definitely - after overcoming her Shrinking Violet phase, she proves to be the most morally well-adjusted of the main cast, dispensing advice to the others on coping with grief after Joyce died. She's also a very understanding and forgiving (without being a doormat about it) lover to Willow, and becomes the group's Cool Big Sis and Team Mom (especially to Dawn).
Principle Flutie; he was well-meaning, but bumbling. Still, he gave Buffy a fair shake, which is more than can be said for most Sunnydale adults who aren't an English librarian.
Detective Dowling in the comics. He clears Buffy's name, then has Spike show him the world of vampires; Spike takes a liking to him and when asked about Buffy suggests she should be with him. After he tries to take on a vampire nest and is abandoned Buffy does seek him out, but thinks she has nothing to apologize for and his willingness to be Just Friends is enough to upset Spike and Willow over his Angst? What Angst?.
Clem is easily one of the friendliest characters in the series.
In Noah's Arc, Junito is probably the best example, being consistently kind, courteous, patient and understanding with Ricky (who is a promiscuous, emotionally stunted, and often times Jerkass individual).
Despite the fact that that the town of Deadwood is mainly comprised of drunks, slime balls, gamblers, thieves, and murders it has its fair share of nice guys. Chief amount them being Sol Star who manages to be nice to just about everyone in the camp (no easy feat) and to be Heterosexual Life-Partners with the perpetually short tempered Seth Bullock. Other nice guys include Ellsworth, Blazanov, Merrick and Reverend Smith
Dr. Archibald Hopper. He's capable of being civil and helpful to just about anyone. Just don't ask this amnesiac cricket to ignore his conscience or you'll get an earful.
Belle. She seems to be the only person in both worlds who is genuinely nice to Gold, and she goes out of her way to help Grumpy realize that he's in love with a fairy while she's still trying to deal with having her heart broken. Not to mention, she's willing to work with Hook and Regina despite the fact the two have kidnapped, threatened, and generally abused her (though she does call them out on it first).
Prince Charming/David Nolan. He's pretty much Captain America, being a humble, friendly and down-to-earth guy who's also a total badass and The Leader when there's need for one. He did cheat on his wife and cause a great deal of stress to both her and the woman he loves, but that was due to trying to be good in-spite of the effects of the curse.
Bob Ross, host of The Joy of Painting, was well-known for his soft voice and calm, gentle demeanor.
Stargate SG-1 has Doctor Daniel Jackson. He's the moral center of the group, eager to learn about alien cultures and try to see things from their perspective, always advocating for finding a non-violent solution and genuinely being a great friend and good person. Beware the Nice Ones, though, because, even before he Took A Level In Bad Ass, he wasn't afraid to show the Goa'uld just how personal the whole thing was for him. Of particular note is the first season episode where he considers killing a vat full of larval Goa'uld symbiotes but Carter dissuades him with an If You Kill Him, You Will Be Just Like Him speech. He appears to accept this, only to come back and machine gun the container, killing all of the baby Goa'uld.
While all the cast from JAG would qualify, Bud Roberts stands out from the rest as an all-around nice and humble guy.
From Merlin: Merlin, Guinevere, Freya, Lancelot and Mithian are all genuinely nice, sweet-natured people. (Though Merlin grows darker as the series goes on and becomes more and more liable to throw people under the bus in order to preserve his personal vision of the future).
Midshipman Clayton was very nice when he took care of sea-sick Horatio who threw up as he came aboard Justinian, tucking him in a hammock. Later he would bring him a Spot of Tea, or a Spot of Grog, actually, when Horatio had a watch or some responsibilities on deck in the rain. Clayton suffers a fate of many a Mr Nice Guy by becoming... Mr Dead Guy. He fought in Hornblower's stead in Duel to the Death when he felt shamed by Hornblower's bold challenge.
Mariette in "The Frogs and the Lobsters" was such a Nice Girl. She would always hold or cuddle a child to emphasise how sweet and nice she was. How else should viewers know?
In Six Feet Under, Claire Fisher dates a nice boy Toby. Caire and Toby promptly break up when he criticizes Claire's attitude. He thinks she's too cynical and mistaken in believing that her life sucks. Lampshaded when Claire's brother's girlfriend Brenda comments how nice he is (and how he differs from her usual boyfriend type of Troubled, but Cute).
Brenda: Toby seems nice.
Claire:[sarcastic] Yes, Toby is very nice.
Brenda: Not your type, huh?
Claire: A deranged psychopath? No, I guess he's not.
In Glee, Marley Rose is unfailingly nice to just about everyone she meets, even when those people have blatantly insulted her and willingly talked her into an eating disorder out of spite. She does, however, have a breaking point. The girl who stole her boyfriend gets treated with liberal doses of deadpan snark.
Sam Evans is also one of the genuinely nicest guys in the show, particular in Seasons 2 & 3.
Steve Urkel of Family Matters is a klutzy, awkward, annoying nerd who can never take a hint that he isn't wanted around (which he never is). In spite of all of that, he's one of the most genuinely kind, caring, positive, and unflappable people in the world, and would do anything for the Winslow family.
Walter Steele from Arrow to an almost comical degree. He is polite and gentlemanly to everyone. It's almost as though he doesn't realize he's in a Darker and Edgier version of the DCU.
Barry Allen, and the rest of Team Flash, from the spin-off. It makes a notable distinction between the two shows, as Team Arrow is largely built up of well-meaning but flawed people, while Team Flash are largely more well-adjusted good-guys.
Eric Foreman from That '70s Show is a genuinely sweet and nice guy, it's even lampshaded in one episode how he's the only one out of his group of friends to have some kind of moral core. He's even nice to people he doesn't necessarily like when they need his help, such as Jackie when she thinks she's pregnant and Laurie when Red all but disowns her.
Steve Jinks of Warehouse 13 is a genuinely kind, good natured man who very quickly slots into the family dynamic of the show. He's barely on the show for two episodes before he and Claudia become inseparable to the point where he essentially becomes her substitute big brother.
Fabian is kind to the point of being an Extreme Doormat. He is always the one to feel bad for someone being hurt and tries his hardest not to make anyone get hurt. He gets sarcastic and angry at times, but is always a good friend and puts others before himself constantly.
Mick, the series' Lovable Jock. He does have an aggressive streak, but has proven to be a sweet guy who really does care for others deep down. He's also good-natured and supportive, if oblivious at times.
Willow is possibly the nicest person in the house. She's very empathetic and though she's a Cloud Cuckoo Lander, she does pay attention to when people are hurting and tries to help them. She loves animals as well and even tried to make Victor happy.
Trudy, too. She's a very motherly and sweet person who takes care of everyone in the House and genuinely tries to help them when she can. She defends them from Victor as well.
Fitz, probably moreso than Coulson. Besides the time he became a resentful and snappy while recovering from brain damage, he's typically an unassuming, nerdy, submissive, surrogate younger brother to the team.