Absolutely Fabulous: Patsy and Edina, although given Eddie's epic inability to relate to anyone else and Patsy's... well, there've been a few joking suggestions that the "heterosexual" part of the description might not always have been entirely accurate. Patsy sabotaged at least one of Eddie's potential relationships (Saffy called her on it but couldn't stop her) and it's been implied that she was the main reason both of Eddie's marriages broke down.
Adventures In Wonderland: The Mad Hatter and The March Hare in this 90's Disney television series.
The A-Team. Given a Lampshade Hanging when they buy a house as part of a scheme, and the head of the neighborhood watch asks if they're gay. The team has to physically restrain B.A..
The whole team, but Face and Murdock especially. They run scams together, tease each other constantly, they're almost always together in the background (usually goofing off) and Face even tells Murdock "You were always the one I thought I could count on," during a serious argument.
B.A. and Murdock also have this going. With a large helping of Vitriolic Best Buds on the side.
Babylon 5: Londo and G'Kar. An antagonistic example until Season 5.
Band of Brothers: Winters and Nixon, which was true for their real-life counterparts as well. Same goes for "Wild Bill" Guarnere and Babe Heffron.
The book describes this as how the company ended up being. Men would form very close-knit groups of two to four people and those groups would in turn form a closer relationship with other small groups leading to a form of this trope by extension. The TV series doesn't call direct attention to it but it's hinted at in almost every episode with different characters (including replacements). Of course, the entire Easy Company could be said to be one very large version of this trope. Donald Malarkey has stated that not a day goes by that he doesn't thank Adolph Hitler for giving him the opportunity to get to know these men (and most other men of the company expressed similar sentiments while being interviewed for the book).
Apollo and Starbuck from the classic show. Aside from almost always being each others wingmen and even playing on the same team at Triad, both warriors appear to be worried about each other often. Starbuck even gives a hint of jealousy when Apollo is to marry Serina in "Lost Planet of the Gods.
Apollo: Hey. It's me, Apollo. Remember? We talk about things. (in "The Living Legend")
Starbuck is also this with Boomer, and the novelizations state that Adama and Tigh were their generation's Starbuck and Boomer, albeit in a somewhat more serious, responsible fashion.
Of course, Starbuck and both of his life partners form a trio. There's even a secret handshake between the three. Twice.
Boomer: We've been in tighter spots.
Starbuck: We have?
Apollo: And we'll get out of this one, too. I promise.
Battlestar Galactica (2003): Tigh and Adama from the re-imagined show (and in the original version as well, though in a lesser degree). Made abundantly clear by Adama's breakdown over Tigh's revelation that he is a Cylon, though it was obvious before. Saul's own wife even says that William Adama is the one Saul Tigh loves most in the universe.
Howard and Raj. They've had their moments before, but half of the episode "The Cornhusker Vortex" is about them being like husband and wife, respectively. Often lampshaded in the show.
Leonard and Sheldon's relationship is an odd mix between best friends, highly dysfunctional and co-dependent life partners, and parent/child. They have been roommates for a really long time and it's often shown as mutually beneficial.
It is clear that Amy wants to see her relationship with Penny this way, too (and even that the 'heterosexual' part might be negotiable). Penny is more standoffish, however.
Blackadder: Blackadder and Bladrick may be the most extreme example since this relathionship has literally gone on for centuries. While Edmund give Balders a lot of abuse, it's apparent he's at least very used to having him around. One idea Richard Curtis had for a fifth series was "Blackadder as a very fed up and corrupt university don, and Baldrick has been his 'scout' for the past forty years, so in effect they've been married for forty years." (However, the back cover of Blackadder: The Whole Damn Dynasty calls Baldrick Blackadder's catamite...)
Denny Crane and Alan Shore. They discuss their relationship, as well as social opinion of such relationships, frequently. Alan even discussed the English word "love", and how it's a shame that people use it lightly and a further shame that you can't be precise about your meaning, and then firmly applied it to Denny: "I love you." All in a non-sexual way, and yet these two are more intimate than a good number of television married couples. And in the series finale, they do get married, making them literal heterosexual life partners.
The two do end a lot of episodes with some pretty heavy duty male bonding moments—sitting on the balcony, drinking Scotch and...well, without more to go on we'll just have to assume that in this case, a cigar (or rather two cigars) is just a cigar. Probably.
They have sleepovers on occasion, in addition to everything else, and have gone at least once on an extended fishing trip.
Buffy Summers and Willow Rosenberg. It made for a bit of awkwardness when Willow came out as gay, partially because they had grown apart quite a bit during that season and Buffy had no clue until then. It's given shippers more ammunition than every bullet in every war ever.
Angelus and Spike were this at one point. When Angelus got a soul and became Angel they didn't see each other much for about a hundred years. Their mutual hatred of each other (and subsequent Ho Yay) was only escalated because they used to be this trope.
The Closer: Lts. Provenza and Flynn of the LAPD in this crime drama. In fact, it is not uncommon to hear Chief Johnson bellowing, "Provenza and Flynn!!" when she hears about their wacky hijinx (one of which involved a dead body, Provenza's garage, skybox tickets to a Dodgers game, and Johnson more furious than anyone's seen her), and when they're not assigned to work alone, she virtually always pairs them up. A Season 7 episode reveals that Provenza's four ex-wives consider Flynn to be their Fifth Ranger and invite him to their get-togethers.
Brenda: Now don't get angry. Lieutenants Flynn and Provenza...
Pope: Already angry.
Community: Troy and Abed are the epitome of this trope. They even get their own segment during the credits at the end of each episode.
Hotch and Rossi, so very, very much. As the two oldest team members and the Team Mom and Team Dad of the BAU, this is not surprising.
Morgan and Reid also definitely qualify.
When Prentiss was still on the show, she, JJ, and Garcia were a Heterosexual Life Trio example.
CSI: Nick Stokes and Warrick Brown. Similarly, Tim Speedle and Eric Delko of CSI: Miami. Warrick and Nick are another couple that even the actors playing them appear to ship, calling it "good, healthy man love".
Daredevil: Matt Murdock and Foggy Nelson have a bit of this, having quickly become friends upon meeting at Columbia Law School, sticking together through internships at Landman & Zack before going into business as Nelson & Murdock.
Degrassi: The Next Generation: JT and Toby. Even more so with Emma and Manny, who have been best friends since they were four. At one point in high school, Manny lived with Emma and slept in the same bed. And than when they went to college, Emma made sure that they were roomates. Emma ended up marrying Spinner, who was heterosexual life partners with Jay, who ended up enganged to Manny.
The Master and The Doctor used to be this before they became enemies. Even then, it's sometimes portrayed as a friendly rivalry, with the Third Doctor noting that he looks forward to their next confrontation at the end of the Master's debut story, and the Master once remarking that "a universe without the Doctor scarcely bears thinking about."
The Second Doctor and Jamie, just as their actors were in real life.
You could class the Eleventh Doctor and Rory Williams as this.
Even more so with Eleventh Doctor and Craig Owens. The two times he appeared, despite not being a true companion. The Doctor truly cares about him and admitted Craig as one of his best friends. Heck, a running gag between them is that people keep thinking they're a gay couple.
Dollhouse: In flashbacks shown, Caroline (the future Echo) and Bennett (Echo's future foil) became fast friends in college and were heading in this direction—until a certain bomb went off....
Drake & Josh: The eponymous characters. Also the two nerds Craig and Eric.
Oswald: "So I was drinkin' the other night, and I got to throwin' up and I got to thinkin'..." (long, rambling exposition about him wanting to move back in follows) Lewis: "Hey. You had me at 'throwin' up'."
ER: Mark Green and Doug Ross. To the point where as Doug prepared to resign in disgrace, he mourned the likely loss of his best friend as much as the possible loss of the love of his life, Carol. Meanwhile, Mark almost tearfully declared, "I love him like a brother, but I can't do this anymore. It's too hard."
Faking It: Karma and Amy, right up to the point where Amy kisses Karma to "prove" they're lesbians (It Makes Sense in Context), and Amy starts to have...bigger feelings for Karma...
Flight of the Conchords: Bret and Jemaine live together, even sharing a bedroom if not a bed. Jemaine in particular tends to get jealous of Bret's girlfriends, and they will often accompany each other on dates. The lyrics to "Bret You've Got it Goin' On", which is supposedly a platonic attempt to make Bret feel better about his looks, reveal that sometimes when Bret is sleeping Jemaine puts a wig on him and spoons him.
Frasier and Niles Crane fit this trope perfetly. Granted, they are brothers, but they are also best friends and constant companions. The fact that they act very much like a married couple gets a Lampshade Hanging more than once, and after Niles marries Daphne, he spends as much time with his brother as he does with his wife.
Made all the more clear when Frasier becomes more and more depressed and jealous during the later seasons after Daphne starts living with Niles, who no longer has quite as much time for his brother as he used to, although this is more because Frasier's unreasonably clingy rather than any real distancing, as the two of them fit this trope through the last season:
Roz: I need to talk to you. You're not with Frasier are you?
Niles: Why does everyone treat us like we're joined at the hip? I do have coffee with people other than my brother, you know.
Roz: Oh good, because I'm avoiding him.
Niles: Well then talk fast, because he's meeting me in five minutes.
Chandler and Joey. Roomates who do everything together, up to and including buying joint furniture and raising their chick and duck. Season 2 even has a 'break up' story. While Joey is quite happy when Chandler marries Monica (with whom Joey has a Like Brother and Sister relationship with), he's upset when they announce they're moving away...until Chandler and Monica show him his 'Joey Room' at their house. (Sort of extending it into One True Threesome territory).
Rachel and Monica count having been friends their whole lives but, unlike Chandler and Joey, they don't stay quite as close after Chandler and Monica get together. (Probably because Joey had a lot of affection for Monica, while Rachel didn't get on as well with Chandler). They also drifted apart during their college years.
Fringe: Walter Bishop and William Bell in this show by J. J. Abrams. In Season 3, Alt-Charlie and Alt-Lincoln.
Eddard Stark and Robert Baratheon were this in their youth, though by the time the series begins, they haven't seen one another in nine years. Robert tells Ned that he chose him as his brother over his actual brothers, and Ned is fiercely loyal to him. In "The Wolf and the Lion", Cersei snarks that she's sorry Robert's "marriage" to Ned Stark didn't work out.
Stannis Baratheon and Davos Seaworth. Davos is Stannis's Number Two and is completely loyal to him, and Davos is one of the few people Stannis likes and trusts.
Jon Snow and Samwell Tarly. Jon's actor, Kit Harington, claims that Jon would fall apart without Sam.
Beric Dondarrion and Thoros of Myr. It helps that Thoros is responsible for bringing Beric back from the dead six times.
Rather tragically Deconstructed with foster brothers Robb and Theon—Robb wanted this kind of relationship with Theon, based off the one Ned had with Robert, but Theon ultimately betrays him, which becomes a crucial factor in Robb's death.
General Hospital: Sonny Corinthos and Jason Morgan. Despite the numerous women in their lives, they will always choose each other. Fans call them Sason.
Gilligan's Island has Gilligan and the Skipper. Granted, it's mixed with Vitriolic Best Buds (at least on the Skipper's end), but they bunk together, work together, stick up for each other, and panic when they believe the other is in danger.
Gilmore Girls: Everyone's favorite Mother/Daughter duo, The Gilmore Girls.
Glue gives us two examples Tina and Annie (roommates and best friends), and James and Rob, whose relationship is somewhat rocky but overall very supportive.
Girl Meets World: Riley and Maya. They are both very close to each other, and Riley offers Maya some tips for life's situations.
Serena and Blair. Would rather spend their prom with each other than their boyfriends/love interests.
Nate and Chuck play around with this trope. When the show starts they're this trope to a T, Nate even spending most of his nights in Chuck's bedroom (make of that what you will), but once Chuck falls in love with Nate's ex-girlfriend Blair things turn problematic. During seasons two through four they go back and forth between fitting the trope and being on the outs with each other. Their bad phases tend to begin with Chuck doing something bad and then escalate through Nate being a poor friend. However by season five, and for the rest of the series, they're back to fitting this trope to a T. They also spend most of the series (roughly four seasons out of six) living together.
Greek: Ashleigh Howard and Casey Cartwright. This is most explicit in the final season, when they declare each other to be their soulmates and are both visibly horrified at the idea that their friendship might be a "college relationship".
Has a Patient of the Week and her best friend, who are both runaways from a small religious group, and have pledged to be together "cradle to grave." Too bad one of 'em's dying.
It also has, well, a good portion of the doctors. Yang and Meredith seem to fit this trope best, even though it's actually Izzie (and George, for that matter) that shares an apartment with Meredith.
Christina and Meredith have gotten even closer in later seasons, declaring each other soul mates and more than once sleeping in the same bed. Along with Mer's husband. Their husbands call them "The Twisted Sisters".
Mark and Callie really count as this, despite being opposite genders and Callie being bi. She gives birth to Mark's baby and fully intends for him to raise the baby with her and Arizona (whom she later marries), leading to one of the most beautiful family dynamics on the show. And then Mark dies.
Not to mention Derek and Mark, once they finally moved past that whole Mark-slept-with-his-wife thing. Derek and Owen are somewhat this as well, though there is a hiccup during the time Derek blames Owen for the plane crash. He moves past that eventually though.
Mark even admits later that he came to Seattle to get Derek back not Addison. He has no other friends (until Callie) and even considers Derek's mother to be his surrogate mother. Not that it stops him from sleeping with Derek's sisters (one for sure and one implies it).
Hannah Montana: Miley and Lilly. So much so that, in the series finale, neither appears fazed by leaving their boyfriends, but can't stand the thought of leaving each other. Their decision of where to go to college was heavily influenced by where the other would go.
Hawaii Five-0: Steve and Danny were initially Vitriolic Best Buds (with Danny in particular constantly complaining about Steve), yet they simply cannot seem to spend enough time together, to the extent that their work and personal lives have no separation at all. Steve is an Honorary Uncle to Danny's daughter Grace. They are both willing to die for (or simply with) each other. Also, they Man Hug regularly and recently they have taken to openly saying "I love you" to each other.
Heroes: Hiro and Ando. In one episode, Ando even commented, "That is how we roll." As a reply to something to the effect of, "You guys go to the bathroom together...?" Hiro used the same words in response to Ando saying, "You came back for me." It helps that he has a thing for Hiro's sister.
Highlander: Has several: Mac and Richie, Mac and Joe, Mac and Connor, all four Horsemen, arguably Mac and Methos....
Horatio Hornblower: Horatio Hornblower and Archie Kennedy — and as has been mentioned under "Literature," Horatio and William Bush later on. During Mutiny and Retribution they form a Power Trio, until Archie is killed.
House and Wilson. In the second and third seasons, the writers make light of the shipping.
Stacy: What are you hiding?
House: I'm gay. (Stacy glares at him) Oh! That's not what you meant. It does explain a lot though. No girlfriend, always with Wilson, obsession with sneakers...
Considering that the creators have said that there is a decent chance that House will end up with Wilson, and that Hugh Laurie ships it, the heterosexual part of this trope is highly debatable. It seems possible that House/Wilson could become canon.
The fourth season goes well beyond "making light of," as House ends up demanding visitation rights from Wilson's new girlfriend.
"My God! You're dating me!"
That season also implies that House tries to sabotage Wilson's relationships so that he won't lose him to a woman.
5th season, Cuddy puts House and Wilson in "couples therapy" because Wilson doesn't want to be House's friend anymore.
On the 6th season, House moves in with Wilson, and it seems that they're actually going to stay together for a while.
In the final season, Wilson is diagnosed with terminal cancer and has five months to live. Meanwhile, House just earned himself a six month jail sentence. What does he do? Fake his own death, meaning he can never practice medicine again, just to spend Wilson's final months with him.
Probably the longest running gag in the show, starting from the pilot, is Marshall and Barney's never-ending, recurring turf war over which of them is Ted's best friend (it's always Marshall, but Barney doesn't take "no" for an answer).
Played With as well: good bit of the first and third seasons' undertones is Ted coming to terms with the fact that he and Marshall can't be the exact same dynamic duo they had been since college anymore now that Marshall's marrying Lily (although it doesn't negatively affect their friendship — it just alters it a bit) and gravitating towards Barney in his quest to meet the woman he'll marry. In "Okay Awesome", after Marshall worries that Ted might be drifting away from him now that he's engaged, Ted says he wants nothing more than to do fun couple stuff with Marshall and Lily, but he can only do that if he himself is part of a couple too, so he has to first run around doing stupid single things with Barney in order to meet enough girls to find "the one". However, halfway through the third season he realizes what a horrible influence Barney is on him after spending a night behaving like a sleazy, Barney-esque jackass, and since then has firmly stuck to Marshall as his best friend and role model, although he has admitted that Barney is for all intents and purposes his brother.
As for Barney, he considers himself to be Ted's best friend. Ever since meeting Ted, he has immediately latched on to him and is constantly bothering him to hang out. When Ted finally gets sick of it note although Barney sleeping with Robin certainly didn't help and breaks off their friendship, Barney is heartbroken. Then, when he catches word that Ted's been admitted to the hospital he runs from work to get there. He almost makes it too, before he gets hit by a bus. Ted welcomes him back into the group after that. The sad thing is, it's implied that Barney's past and self-problems force him into a state of complete denial, causing him to act the way he does. Ted and the others are the only things keeping him from going too far.
As stated above, Barney runs all the way to the hospital Ted is in in the third season finale "Miracles", only to be hit by a bus and sustain injuries far more serious than Ted's. Afterwards, he, Marshall and Ted have a moment Ted later admits got really mushy, which involves all three of them crying and hugging while exclaiming they are brothers.
Lily and Robin could be this (they've both declared the other their best friend and clearly stay very good friends in thirty-odd years) if it weren't for Lily's undisguised crush on Robin.
Mac and Dennis. The two live together, work together, spend all their free time together, and check in with each other several times a day to make sure the other is okay. The commentary for "Mac and Dennis Break Up" has the staff (possibly jokingly) talk about the fact that Mac and Dennis are possibly gay and in a pre-sexual romantic relationship that neither is completely conscious of.
Charlie and Frank might also qualify for this, but they're freaky beyond description, so it's hard to say either way.
Dee So you don’t think that two thirty-year-old men who spend every waking moment together is a little bit pathetic?
Jackass: Chris Pontius and Steve-O sometimes give off this vibe, especially inasmuch as they eventually got their own show together, Wildboyz. Watch the "shark-fishing" skit in the second Jackass movie, when Pontius is helping Steve-O get the fishhook through his cheek. Pontius seems to be having sympathy pains.
Most protagonists and their deuteragnists have this dynamic.
Shinji and Ren are more often at each other's throats than not, but they do have their odd moments together. Especially when Shinji dies.
Kenzaki and Hajime are very similar to the above, and likewise it's hard to deny the depths of their friendship when the former turns himself into a monster so the latter can continue to live among humanity.
Yuuki and Tomoko from Kamen Rider Fourze, though at times Tomoko's reactions come off more like a Stalker with a Crush. This trope applies even more to their actresses Fumika Shimizu and Shiho; in the Fourze Quiz segments included on the DVDs, they tell each other "I love you" a lot, and when they're on the same team they spend most of the short holding hands, semi-snuggling, giggling, and whispering to each other.
Keen Eddie: The professional friendship between Eddie Arlette and Monty Pippin is a prime example. Mark Valley: "You got to admit, whenever two guys have to spend an awful lot of time together, the question is going to come up. There's always that thing of, 'Oh my God, are we gay?' Like, not physically, but you're enjoying each other's company — you know what I mean? It could be read that way, and we joke about it, but they're just two regular guys hanging out, spending an awful lot of time together."
Life on Mars (2006)/Ashes to Ashes: Ray Carling and Chris Skelton, although as of season 2 the hints have been flying thick and fast that there might be a little more than that going on with Ray's chronic resentment of Chris's girlfriend (which admittedly got better during the third season—the resentment, though, not the hints). To wit, Alex's letters for the entire team to be opened in the event of her departure; everyone opens theirs right away, and all we hear about Ray's is that it contains the word "repressed." This bit of dialogue from the season 3 finale:
Shaz: Don't panic, Ray. I ain't going to be no gooseberry. Blimey, I'm amazed you two never tied the knot. Chris: It's legal in Holland. Ray: Can we talk about something else like...women, or snooker?
Lost Girl: Kenzi and Bo are a clear example (though Bo isn't heterosexual). They are roommates for most of the show, and very clearly the most important people in each other's lives. Both have put themselves into incredible danger to help the other one out. So much so that it is Kenzi, and not either of Bo's love interests—Lauren or Dyson—who counts as Bo's "heart" when it comes to magic.
Kenzi: No, Dyson; she loves you, yes; she loves Lauren. But you know that it's me. I'm her heart, you know that.
The Middleman: Wendy and Lacey. Years later the actresses were hired(?) by David Lynch to have an epic romantic falling out in a music video.
The Mighty Boosh: Howard Moon and Vince Noir. They work together, live together, go on adventures together, throw satsumas (tangerines) at each other in the snow while wearing only underwear together...Vince is also often mistaken for Howard's girlfriend or wife (since Dude Looks Like a Lady). Lance Dior claims to have heard that Howard is Vince's wife, that he cooks his meals, cuts his hair, and bakes him "little cakes". The relationship remains strictly platonic, despite a few close calls. Once (infamously) in Party, and once in Boosh Live, when Howard's technique with the ladies is described by Vince as a rude invitation to get into his wheelbarrow (he's from Leeds, you see). Howard protests, claiming he was drunk, and Vince laughs, "I know, so was I — I was in the wheelbarrow."
This show make this older than a LOT of people think, apparently. As do Flanders and Swann.
Morecambe and Wise were always shown as very close and as quarreling like an old married couple, but were reluctant for years to do their first sharing a bed skit, even though their relationship is clearly platonic.
Supposedly they were both immediately brought round to the idea by one of their writers pointing out that Laurel and Hardy shared a bed on film.
Muppets Tonight: Pepe the Prawn and Seymour the elephant. They were stage partners and did almost everything together. Though while Pepe went on to star in more muppety stuff, Seymour was put on a bus.
The Naked Trucker and T-Bones: In both their live stage show and the short-lived television show.
The Nanny: Fran and Val. They've been best friends since kindergarten, spend almost all their free time together and even took each other to prom. In one episode where a Cambodian girl they sponsored in high school comes to town they almost immediately begin acting like a married couple with a teenage daughter, even going to couples counselling.
Val once implied that she occasionally had sexual fantasies about Fran.
"Guilty Pleasure" lampshades this one with Tony and McGee (Ziva provides the lampshades). The two have a falling out (which Ziva describes as a "seven-year itch") during which Tony spends a lot more time working with Phil McCadden, scheduling "hang out time" together after hours and starting to dress the same. But after McCadden dares insult McGee's skills as an agent, Tony backs away and is soon back by McGee's side, refusing to answer McCadden's calls.
Meanwhile, Gibbs and Fornell visit each other's houses with offers of dinner on the pretense of exchanging case information that could have been traded over the phone.
Gibbs and Ducky. They've worked together for years, and Ducky's the only person who gets to call Gibbs "Jethro".
Gibbs and Franks.
NCIS: Los Angeles: Callan and Sam are this trope, written that way intentionally, even to the point other characters make comments about them being a married couple.
Neighbours: Harold and Lou. They actually started off as fierce love rivals but now they're like an old married couple. Also, from the same show, Steph and Libby.
New Girl: Nick and Schmidt. To the point of Schmidt throwing a wedding-like party to celebrate their having been roommates for ten years. At least one guest had to explain to his mother that despite what it sounded like they were not a couple.
also Jess and Cece seem to be this, having been friends since grade school
Night and Day: Cohabiting chums Dennis Doyle and Sam Armstrong spent much of the series sharing a double bed.
Nip/Tuck: Sean and Christian have been best friends and colleagues since college, and Christian is godfather to Sean's children. The show does actually explore the possibility of Christian having repressed homosexual feelings for Sean when he starts having dreams about them being lovers, but they both conclude it doesn't really mean anything.
North and South (Trilogy): The two principle characters of the series, Orry Main and George Hazard. There is also Orry's cousin, Charles Main, and George's younger brother, Billy Hazard. Of course, things get awkward when the two brothers end up siding with the Union and the cousins with the Confederacy when the Civil War kicks off.
NUMB3RS: Colby and David fit the trope to a "T", even displaying jealousy at each other's outside friendships and acting heartbroken when one or the other is removed from the group.
Falani and Eric during season six, this being outrageous fortune everyone ignores the first word when talking about them.
The Old Guys: Tom and Roy, mostly by process of elimination (spousal death, divorce and being incredibly unlucky with women).
Once Upon a Time: Red and Snow. They meet when Snow is fresh on the run from her evil stepmother, and remain close friends until the curse takes them. At one point Red even risks her life by going into wolf form to give Charming time to escape and find Snow. It helps that it's also implied that Red's grandmother ends up being a Parental Substitute to Snow.
One Tree Hill: Brooke and Peyton. Also, Marvin "Mouth" McFadden and Antwon "Skills" Taylor.
Oz: Busmalis and Rebadow. Despite Rebadow once trying to kill Busmalis, they've got the "old married couple" thing down pat.
Pawn Stars: Chumlee and Corey. Despite the fact that Chum annoys Corey, they care about each other.
Peep Show: Mark and Jeremy. In the season 5 finale, Sophie is pregnant and it might be either Mark's or Jeremy's. Mark comments on Sophie's increasingly erratic behavior and says that if she continues like that, they can just adopt the baby "like those gay dads"
Jason and Tommy. Several seasons had the Red Ranger have this relationship with the Sixth Ranger. Funnily enough, this went both ways with these two: in the first season, Jason was Red and Tommy was Sixth; in Zeo, Tommy was Red while Jason was Sixth (a replacement Sixth, but still).
Emerson and Ned qualify as well. Not only do they work together on Emerson's PI cases, but in the process of working those cases they come to know each others' deep, dark secrets which ultimately connects them on a personal as well as a professional level.
Quantum Leap: Sam Beckett and Al Calavicci. Al is about the only thing from his time Sam consistently remembers throughout the series, and both of them sacrificed a lot for one another.
Although Olaf Petersen only makes a handful of appearances, a strong impression is given that, before the accident, he and Lister were Heterosexual Life-Partners. Lister apparently has a tattoo that says "I Love Petersen".
Rimmer and Lister could be considered involuntaryHeterosexual Life-Partners; there's simply no-one else for them to talk to. They live (well, in Rimmer's case, exist) in a mile-long abandoned spaceship, but still sleep in their old crew bunks in the same room.
Revolution Sebastian Monroe and Miles Matheson, who grew up together and call themselves brothers, though it seems that Bass is much more dependent on Miles as several characters mention his Sanity Slippage after Miles leaves him
Maura Isles and Jane Rizzoli of the eponymous crime show. Oh, boy, Rizzoli and Isles.
Rizzoli gets threatened by a serial killer? Goes to stay with Isles. Isles' friend gets killed? Reaches straight for Rizzoli. Eat together, run together, have drinks together, Fight Crime(!) together, far and away each other's Most Important Person. Isles is the product of a Friendless Background: she has never had a best friend before Rizzoli, and has a worrying tendency of pointing out to any potential Love Interest that they have a dire, undiagnosed medical condition—Rizzoli claims that men either run away from the badge or want to misuse the handcuffs. Some people see Les Yay, others merely intense friendship, but either way, very, very close—and hilariously codependent. They can't seem to do a thing without each other.
Scrubs: J.D. and Turk. They've been friends since college and their friendship is so strong that Carla has said sometimes she's afraid that Turk will leave her for J.D. They're so close that most of the recurring or one shot characters have thought they were a gay couple at least once.
When Turk and Carla came back to work after their honeymoon, JD acted like he'd been gone for years. Turk evens gives his new wife a "Can I go play with my friend?" sort of look before running to hug him.
Seinfeld: George and Jerry. Not that there's anything wrong with that.... They even go as far as to spend large part of an episode on George having a girlfriend who looks an awful lot like Jerry. It turns out to be more than he is able to handle, though.
The Sentinel: Jim Ellison and Blair Sandburg; Blair actually moves in with Jim early in the series.
It's clearly visible in the scene where Jim tries to revive Blair, who was shot by Jim's Evil Counterpart.
Sesame Street: Bert and Ernie, and many a joke has been made about this one. Word of God says that Bert & Ernie were originally conceived to be brothers, but the show's creators saw more storyline potential with them as an Odd Couple pairing.
In Shadowhunters, being parabatai is the Shadowhunter version of this: It means that two warriors fight together as one, with their hearts beating in unison. When one dies, the other immediately knows it. Jace claims that it's stronger than any human bond, but Clary counters that she has the same kind of bond with Simon.
Shake It Up!: CeCe and Rocky, who do absolutely everything together, and have the same hopes and dreams. Reinforced by Rocky's refusal to be on the show if CeCe couldn't be on.
Sharpe: Richard Sharpe and Patrick Harper. After brief enmity and beating the crap out of each other, they settle into a friendship that leads them to walk into combat zones for each other after they each leave the army, and the exchange "Are you with me, Patrick?" "Yes, always." There's a strong implication that when Sharpe is should-be-mortally wounded, he only lives because of Harper's determination that he will.
Sherlock: Sherlock and John, in keeping with their historic portrayals, as very much this — especially by the end of the second season.
Irene Adler even points out that they're a couple. When John once again claims that he's not gay, Irene simply says it doesn't matter. In fact, she's gay but still has a thing for Sherlock.
The Secret Circle: Faye and Melissa. Also Diana and Cassie, though they’re later revealed to be sisters.
Skins: Go to the show page for a short list of these friendships.
Sonny with a Chance: Nico and Grady, even with their own 'breakup' episode where they try to replace one another with Sonny.
Spaced: And just so nobody has to go looking for it elsewhere in the article...Tim and Mike.
Spartacus: Blood and Sand: Spartacus has has two. In Blood and Sand it is Varro. In Vengeance and War of the Damned it is Agron. The latter is actually gay, but in that place and era this kind of detail mattered a lot less since Agron was a Manly Gay and he and Spartacus were Bash Brothers.
Sports Night: Casey and Dan. Though each has some significant romantic relationships, their most sustained—and sustaining—relationship is with each other. When Dana screws up her relationship with Casey, it's Dan who knows exactly how and why she went wrong. A painful estrangement, based on professional status and hurt feelings, between the two men is resolved during a Passover seder, at which Kasey confesses that the years he has spent working with Dan have been the best of his life, and he wouldn't trade them for anything.
Stargate SG-1: Jack O'Neill and Daniel Jackson. The shipping that results is lampshaded in episode 200.
Stargate Atlantis: John Sheppard and Rodney McKay don't lack in this trope, either, with Sheppard's actor, Joe Flanigan, joking that the closest Sheppard ever came to a girlfriend on the show was McKay.
Starsky & Hutch: The title characters. Very much. Both of their actors even refer to the show as a love story between two men.
Kirk and Spock, as well as Kirk and Bones. Kirk and Spock's relationship grew exponentially over the course of the series, while Kirk and Bones were established to have been VERY close from the first episode, with their friendship reaching farther back than Kirk and Spock's. To say nothing of Spock and Bones.
Their counterparts from the J.J. Abrams movie were set upon by the plot that they must end up like this. (Except less slashable, if J.J. has anything to say about it.)
Chekov and Sulu are depicted this way in Star Trek V: The Final Frontier. Oddly, the rest of canon doesn't really show them to be more than friends and colleagues, though their relationship is expanded upon in some of the tie in novels (where for example Chekov is Godfather to Sulu's daughter).
Had Julian Bashir and Elim Garak; both actors remarked during interviews that they had deliberately played up the homoerotic undertones of the characters' relationship, and Andrew Robinson later wrote a novel, A Stitch in Time, about Garak's life in which he clearly depicted the alien Garak as bisexual. Later, when Paramount script writers had abruptly put an end to the Bashir and Garak subplots, Doctor Bashir and Chief O'Brien spent so much time together on various projects and on hobby activities that O'Brien's wife Keiko complained about it. They have an argument over it where Bashir says he's wildly in love with Ezri (female, now) but he "likes [O'Brien] more", and O'Brien doesn't feel the same.
O'Brien may not immediately reciprocate Bashir's feelings in this scene, but there's another earlier scene where the two are discussing an argument O'Brien is having with Keiko, in which O'Brien says something to Bashir like "Why can't she be more like—" and though he breaks off and then ends with "— a man," it's obvious he was going to say "you." It's fairly obvious from the conversation that O'Brien feels the same way, even if he can't admit it to Julian. Which is a hallmark of their relationship.
Then there's the young Ferengi Nog with his human pal, Jake Sisko.
Strange as it may sound, there's an element of this to the friendship between Benjamin Sisko and Jadzia Dax. While she's an attractive young woman now, he still relates to her as his older male mentor, to the extent that his nickname for her is "Old Man".
Star Trek: Enterprise: There's Captain Archer and Trip Tucker. Their hearty attitudes were frequently a source of confusion to mess hall companion T'Pol, though even she recognized the loyalty the two had for one another. When Trip's fears about the Xindi attack on Florida were confirmed – that his sister was among the casualties – the swiftness with which Archer had his buddy's back (“Whatever it takes”) is simultaneously enthralling and chilling. In addition, Trip develops this relationship with Malcolm Reed, being the only one that Malcolm feels comfortable opening up to.
Data and Geordi. Both of these guys bonded over their love of science's gadgets and gizmos, and could busy themselves for hours tinkering and theorizing. Considering that Geordi's firsthand knowledge of human feeling often made Data something of the pupil, it's no surprise that these two are frequently seen together.
Picard and Riker, in a lesser extent. Both would usually hang out during their free time, and it is Riker who become Picard's surrogate father in one episode where Picard and three others were de-aged.
Dean and Sam Winchester can be seen as a literal case of this, since they've spent most of their lives with each other on the road, Dean having practically raised Sam. Not to mention the fact that they're apparently "soul mates", making them Heterosexual Afterlife Partners as well. The show's creator, Eric Kripke, jokingly referred to Supernatural as "The epic love story of Sam and Dean".
Dean telling him this was in response to Sam attempting to finish the trials—which would result in his death—because he didn't want to let Dean down. There's a reason these guys have been referred to in-show as "psychotically, irrationally, erotically codependent on each other".
Survivor: Tocantins: Stephen and J.T. were constantly referred to as the "BFF Boys" or borderline boyfriends by fans during their season. J.T. certainly manipulated the emotions of their friendship to his advantage at Final Tribal Council to win himself a unanimous victory, if later interviews and commentary are any indication.
Teachers: Brian and Kurt from this British series are even commented on for acting very similar to a married couple. They rarely have any screen time apart, even when one of them is in a semi-serious relationship. They also share a flat with each other.
Scott and Stiles have been best friends since kindergarten and stay at each other's side through everything, from turning into a werewolf, asking out a girl, being possessed by supernatural creatures or making the lacrosse team. According to the actors, their closeness is partly because they're both missing a parent and depend on each other more because of it. Hilariously the other characters are all too aware of how inseparable they are, and the only effective punishment their parents and teachers have is separating the two of them. And that's not even mentioning the amount of times they put their lives on the line for each other, one episode has Stiles risking his life to talk Scott out of committing suicide, while Scott's Love Interest is standing right there. The two of them also plan to live together after leaving home, even though they both have serious girlfriends by this point.
Stiles: "Scott, you're my best friend and I need you. You're my brother. If you want to do this, you're just gonna have to take me with you."
Allison and Lydia also develop into this.
Jackson and Danny (subverted slightly in that Danny is gay, however, he hasn't the slightest attraction to Jackson as anything more than friends—which, somewhat hilariously, annoys Jackson, as he sees himself as being everyone's type.)
Danny: I'm supposed to watch you in bed? You remember all the times I told you you're not my type? Jackson: Just do it. Oh, and FYI: I'm everyone's type.
Also, as of season 4, we have Liam and Mason. It was feared that they would be Jackson/Danny 2.0 (and in a sense they are, with Liam being straight (as of so far) and Mason being gay) but soon shown to be baby Skittles—and making them very important to the fandom with their preciousness.
Twin Peaks: Special Agent Dale Cooper and Sheriff Harry S. Truman have a real bromance going on. Despite their very different characters they are endlessly patient with each other. In fact, they are visibly appreciative of each other's differences. Gazing, tender smiles, nose tweaking—it's all there.
Viva la Bam: Bam and Novak generally refer to each other as 'life partner' for the laughs, seeing as they were attached at the hip.
Jed and Leo are practically the embodiment of the trope, spending almost all their time together, having several old married couple-like moments, engaging in tiffs and squabbles that never stick, talking excessively and pointlessly, getting antsy and downtrodden when separated, etc. They were friends many, many years before Jed became the President of the United States and Leo his Chief of Staff and closest advisor, and therefore their working relationship (which takes up the vast majority of their waking hours) fits their friendship like a glove.
Jed even teases Leo about it!
There's a rather hilarious moment in one of the season one DVD Extras where Martin Sheen and John Spencer agree that they're the "parents" of the True Companions that is the main cast, but each believe that they're the husband and the other is the wife. (This troper is fairly sure that someone affiliated with the show called Abbey and Leo the President's "wife and mistress" at one point).
Sam and Josh as well, until Sam was written out and Josh got more focused on Donna.
Also, Ed and Larry, in later seasons. This pairing is the most obvious in the series, especially once many characters admitted that they weren't certain which was Ed and which was Larry, they were simply 'Ed and Larry.'
White Collar: Neal Caffrey and Peter Burke of this USA show definitely fit the bill, as Neal is a CI under Peter's watch for a four-year term. Peter even says "For the next four years, I own you." Though they start out antagonistic with each other, as the series has carried on, they have shown more and more care for each other. Most recently, when Peter was kidnapped, Neal turned over a ring that he had saved for his late girlfriend, Kate, as ransom.
Hell, when Neal is about to flee the country with Kate, Peter finds them and asks Neal to stay. Neal ends up choosing Peter. And then the Big Bad kills Kate because of this.
Neal and Mozzie. Mozzie started out as Neal's mentor when Neal first moved into New York, but this grew into a very close relationship. Despite this, there's much about one another they don't reveal.
Whose Line Is It Anyway?: Colin Mochrie and Ryan Stiles. They've been working on the show together for decades and both of them have admitted on several occasions that the other one is their best friend
The Wild Wild West: James West and Artemus Gordon, who live, work, play, go on double dates and generally do everything together.
Herc and Carver for at least the first four seasons (maybe), complete with bickering.
Bunk and McNulty, definitely, although some might argue that it's simply because nobody else can drink as much as they can.
The best case, though, for most of the series is Avon and Stringer. Friends from childhood, they ran their empire together, and could be counted on to come through for each other despite disagreements; it was almost as if they were married. Of course, a lot of marriages end badly....