Science Ninja Team Gatchaman: "Condor" Joe Asakura, a.k.a. G-2. In the beginning, he's a Sociopathic Hero constantly undermining Ken's authority because he wouldn't let Joe go on the attack. But by the second half of the first series, Joe's the only one who's able to talk Ken down when he MAJORLY Freaks Out after Red Impulse, Ken's long-absent father, is killed, showing they have a Ryu And Ken (the Capcom ones) style respect for each other. From the beginning, he has a serious vendetta against the antagonists of the series since ''his parents are Deeaaad!'' thanks to them, which drives his Anti-Hero tendencies, and true to his role, he's the member that ends up dramatically dying in sacrifice at the end. of the first series at least, subverted in the sequels.
In the 90s Sailor Moon anime, Rei/Sailor Mars is The Lancer of the team. The DiC English dub exaggerated this into a running subplot of her trying to subvert Usagi's leadership. In the manga, however, the Lancer is Minako/Sailor Venus, the leader of the Senshi in the Silver Millenium and the most seasoned warrior of the group. In some ways, manga Minako is an example of The Hero unto herself, with Rei being her Lancer rather than Usagi's.
Trigun: Nicholas D. Wolfwood to Vash the Stampede. Wolfwood and Vash work incredibly well together and often appear to be two of a kind when goofing around or actively engaged in combat, but have deep philosophical differences. Wolfwood is dark: a killer and Knight in Sour Armor with a secret agenda. Vash is a Technical Pacifist and All-Loving Hero. They're keeping huge secrets from one another, and they know it. They're still the best friends either has ever had. Their color scheme contributes.
They get extra bonuses in the manga, with Foil elements like the fact that, even though they look the same age, Vash is Really Nearly Two Hundred and Wolfwood has accelerated aging from the experiments the Eye of Michael did on him, and based on his former orphanage-mates can't possibly be even eighteen. Also, he joined up with Vash because the Big Bad told him to.
Pretty Sammy: Pixy Misa becomes this in near the end of the series.
Gantz: Kei Kurono was undoubtedly The Lancer to The Hero Masaru Katou, his old friend. Until Katou died and Kurono became The Hero instead, whereupon Izumi becomes his Lancer. Who (plural) at some point got killed off by alien vampires, around the time Katou got revived (the incredibly awesome Osaka arc followed). That lasted till Kei got revived AGAIN, TWICE, so now three heroes are running around, with one of the Kei's and Katou leading a (probably) suicide commando against an alien invasion and another leading humans being held captive by said aliens into freedom.
In a story arc that focused on Katou action girl/the chick Reika got to spend time as his lancer
Corrector Yui: Haruna Kisaragi/Corrector Harunawho was also a Dark Magical Girl for a time. In the second season anime, Control and Synchro/War Wolf are Yui's Lancers when they form a Five-Man Band IR and Rescue. Also, Ai Shinozaki/Corrector Ai is often Lancer-like towards Yui.
Every DigimonFive-Man Band has had a Lancer primarily characterised as a stoicIneffectual Loner to contrast the Idiot Hero, accordingly creating conflict between the two that's escalated with every series; they always eventually overcome the differences, sometimes developing into Bash Brothers. Traditionally they are associated with the colour blue, are either outright blonde or very dark hair, and are partnered with a canine Digimon, though none of these traits are absolute. To date:
Yamato is the series-internal Trope Maker and the straightest example: he and Taichi have a fire vs. ice complement, particularly in later evolutions, and their partners' Fusion Dance into Omegamon creates a guns vs. swords dynamic - the MetalGarurumon arm has a cannon while the WarGreymon arm has a sword.
Digimon Adventure 02 splits the role between Takeru in the first half - focusing on the conflict between himself and Daisuke - and Ken in the second half, focusing on the Hero/Lancer Bash Brothers dynamic and how Daisuke's influence and belief in him pulled him out of a pretty bad part of his life.
Ruki is the only female example, and inverts the standard Digimon dynamic in that while she is indeed the aloof one, she is certainly far more aggressive than Takato.
Kouji's dynamic with Takuya is a direct reprise of Taichi and Yamato's relationship, complete with the guns vs swords contrast in their strongest forms, which were even a Greymon and Garurumon respectively.
Touma's contrast with Masaru is played up mainly in respect to intellect and approaches thereof - Touma is The Chessmaster, while Masaru... isn't.
Kiriha, like Ruki, embodies something of a reversal of tradition - Taiki is a brilliant strategist; Kiriha isn't a slouch in that department, but is certainly much more of a Blood Knight. Incidentally, this time Kiriha is the one with a Greymon.
Yuu is easily the lightest example - there is some rivalry between him and Tagiru, but it's barely given any attention whatsoever... much like Yuu himself.
Dragon Ball Z had several through the show's run (including Krillin, Yamcha, and Tien), though two stand out more prominently:
Piccolo is Goku's arch nemesis before pulling a Heel–Face Turn. He functions as the Leader during Goku's many absences, being the more rational and levelheaded mindset to contrast with Goku's outgoing, charismatic personality.
Vegeta is The Rival and the Token Evil Teammate to Goku, along with pulling off a Red Oni, Blue Oni. He is aloof, irate, and perpetually serious as a foil to Goku's fun-loving, easygoing Fun Personified characteristics. As the series goes on Goku starts to look to Piccolo primarily for counsel, but to Vegeta to be his right hand man on the battlefield.
Almost all the characters in Soul Eater have a tendency to play off of eachother, switching from Hero to Lancer when the plot calls for it.
Sanosuke Sagara in Rurouni Kenshin. He starts out as Kenshin's rival before quickly becoming his best friend, spent the gap between the revolution and the start of the series as a glory-seeking street fighter rather than an atoning wanderer, and prefers hand-to-hand combat over disciplined sword fighting (although he was skilled with his BFS, which he lamentably only used twice).
Until his departure, Brock played The Lancer to Ash in the Pokémon anime, though not the games (which are a different universe entirely).
GoLion did an interesting bit on this trope. While Isamu Kurogane was named LANCE by Voltron fans, he was not the original Lancer of the team. . . that job was temporarily held by Takashi Shirogane (Sven).
Gray of Fairy Tail, given his rivalry with Natsu and their complementary elemental magic (Fire and Ice). He even used to be The Rival.
Natsuki Kuga is Mai's Lancer in Mai Hime, being both her Foil (Mai is very strait-laced, while Natsuki's willing to break a few rules to meet her personal objective) and opposite number in the Elemental Powers department (Mai uses fire, and Natsuki uses ice).
Jet Link aka 002 is Joe Shimamura aka 009's Lancer in Cyborg 009. Albert Heinrich aka 004 and Francoise Arnoul aka 003 sometimes fits in, too.
Guts filled this role for Griffith in Berserk when he was still part of the Band of the Hawk.
After The Eclipse, Guts became the head of his own travel group and Serpico now fills this role for him and displays the typical antagonism of this archetype, at least until Guts definitively defeats him in Vritannis. Serpico then learns to trust his de facto leader and to work effectively alongside him.
Snagglebit in the obscure 1990s anime The Littl' Bits fit this trope to a T.
Eiji Shigure in Gravion may be the main character of the series, but is arguably the Lancer of the Gravion team, and often fills in the role with main pilot Toga. An odd variation of that, as while Toga is definitely the more pure-hearted of the two, he still depends on Eiji to keep him morally grounded in battle.
One could also make a case for Sanji being the Lancer: a similarly cool personality, like Zoro's, contrasted with Luffy's, but also, as per the "He's the one who sneaks off on his own to advance the team's goals independently" bit in the description, Sanji has done just that on at least four occasions (Little Garden, Alabasta, Water 7 and Enies Lobby). Sanji also fits as lancer for his perv status in contrast to Luffy's Chaste Hero status.
There are several (and very different, personality-wise) Lancers in the Gundam meta series:
Gundam 00: Lockon Stratos, to Setsuna F. Seiei. With clear cut Gun vs. Swords abilities.
Gundam AGE: Woolf Enneacle, to Flit and Asemu Asuno. Later, Seric Abis to the third Asuno, Kio.
In Tengen Toppa Gurren Lagann, depending on your point of view either Simon is Kamina's Lancer, or Kamina is Simon's. Upon Kamina's death Kittan gradually qualifes for the role, showing a strong grasp of Kamina's ideals, but lacking the gift with words he and Simon have to express it.
Rossiu is certainly Simon's Lancer after the timeskip. At least until Viral's Heel–Face Turn, at which point Rossiu gradually takes upon a more passive role.
Natsu Tanimoto, a.k.a. Hermit, combines this with a bit of Sixth Ranger to Kenichi: The Mightiest Disciple. One of the last to defect from Ragnarok to Shinpaku Alliance, and then unwillingly, Natsu and Kenichi have the same basic decency but are otherwise polar opposites.
In sports manga/anime, the sub-captain of the team is likely to be The Lancer to the captain. Either that, or The Rival within the team plays this role for The Hero (who isn not necessarily the captain). Examples:
Seigaku: Oishi and/or Fuji, to Tezuka. Momoshiro, to Echizen and later, to Kaidoh
Fudomine: Kamio, to Tachibana.
Saint Rudolph: Kaneda, to Akazawa. Mizuki, to Yuuta (as a good example of a sneaky Lancer who uses less-than-ethic methods).
Hyoutei: Shishido, to Atobe; he actually took one for the team during the yakiniku battle (sacrificing himself by drinking Inui juice so his team could go on). Ohtori, on the other hand, is Shishido's own Lancer (which makes them also a very popular Ho Yay subject, even lampshaded once or twice in the Dating Sims).
Isn't Oshitari more of a lancer to Atobe? Besides Kabaji, Atobe is probably closest with him, often leaving important duties with him. They are also both All-rounders, coincidentally.
Yamabuki: Sengoku and/or Dan, to Anti-Hero Akutsu.
Rokkaku: Saeki, to Aoi.
Jyousei: Wakato, to Kajimoto.
Rikkaidai: Sanada, to Yukimura. Also, Renji to Sanada
Higa: Rin, to Kite.
Shitenhouji: Chitose (also Sixth Ranger), to Shiraishi. Koishikawa was supposed to be The Lancer, but Chitose's appearance shot that to Hell.
Depending on the team he's playing, Tsubasa can hace several Lancers. Up to date: Ishizaki, Misaki, Wakabayashi, Hyuga, Pepe and/or Rivaul.
Wakashimazu and Takeshi, to Hyuga.
Oda, to Matsuyama.
Müller, to Schneider. Sometimes Schester too, though he's more of The Smart Guy A small subplot in Road to 2002 had Schneider trying to personally recruit Wakabayashi as his Lancer, too.
Napoleon, to Pierre.
Pascal, to Juan Diaz
Kaltz, to Wakabayashi (in the Hamburg team).
Leo (and briefly, Natourezza), to Santana
Subverted in Slam Dunk, where the vice-captain of the Shohoku team (Kogure) hardly gets any time on the court. Therefore, since we have Sakuragi as The Hero (from story-wise perspective, as he is the main character), he gets Rukawa as his Lancer.
Monta (and later on Riku) is easily Sena's Lancer.
Sakuraba serves as a Lancer to both Takami and Shin, although in some cases Shin could be his lancer (like in the Sagittarius).
Tetsuma is definitely Kid's Lancer, and a damn good one at that.
In a twisted sense of the trope, Agon could be concieved as Unsui's Lancer or Dragon, although a better case could be made for Ikkiyu and Agon switching off as Lancer and Hero/Dragon and Big Bad as well.
Gaou is certainly a Lancer for Marco.
Taka for Yamato, given the fact that the latter is Teikoku's primary ace, but they could be switched without much difficulty
The very proper and by the book Daiuske Shima (Mark Venture) was a polar opposiste to Susumu Kodai (Derek Wildstar) who was originally more impulsive and devil-may-care. Both were also rival for the heart of Yuki Mori (Nova), although Shima quickly conceded, loving Yuki enough to let her go. The rivalry dissapeared completely with the maturing of Kodai and his inheriting leadership as the Acting Captain Yamato (Argo).
Although only slightly older than most of the rest of the crew, chief technician Shiro Sanada (Sandor) was Yamato's elder figure after the deaths of Captain Okita (Avatar) and Engineer Tokugawa (Orion). Sadly, Shima makes the ultimate sacrifice that many anime Lancers are known for. However, interestingly enough, in Yamato:Rebirth anime, Sanada actually becomes EDF Supreme Commander, in effect becoming Captain Kodai's superior officer; the rare case where the Lancer eventually gets promoted to outrank the Hero (even if it took 25 years).
Kuwabara from YuYu Hakusho. He's Yusuke's school rival-turned-best friend, frequently teams up with him for tag-team battles, and leads the Team Urameshi almost as often as Yusuke does in the Dark Tournament saga.
Thanks to Yes! Pretty Cure 5's insistence on dual-classing everyone, Nozomi has both BigLancer Rin and SmartLancer Karen to contend with. They manage to simultaneously act as foils for both Nozomi and each other. The former is the better example.
Fresh Pretty Cure! has two. First it was Miki who later became the Big Guy and is replaced by Setsuna who doubles as a Smart Guy. The latter got closer to the heroine Love and has become even a part of her family.
Similar to Yes!5, Smile Pretty Cure! has the BigLancer Akane and the SmartLancer Reika to Miyuki. While the former has a closer relationship to Miyuki and has the greatest physical strength, Reika has defeated Joker twice.
In Doki Doki Pretty Cure, despite that Smart Girl Rikka is Mana's best friend for years, Makoto fits to the Lancer role better. She has the most counts of defeated Jikochuus after Mana, is one of two offensive Pretty Cures (the other is Mana) and is a serious veteran who acted as an Aloof Ally early in the series.
Chrono in Chrono Crusade serves as Rosette's lancer (particularly in the manga where Rosette is firmly the protagonist). While they usually seem eye-to-eye on moral issues, and they are in fact the Official Couple, they often clash and get into arguments—Rosette is hotblooded and determined, while Chrono appears to be calmer and also slips into despair much easier. Rosette is a nun, and Chrono is a demon. Rosette is very open with her emotions, while Chrono tends to try to hide when he's upset.
Higurashi: When They Cry has an interesting example in Keiichi. He starts off as a Decoy Protagonist, is a bit paranoid and actually steers into Villain Protagonist territory. In later arcs, the spotlight switches to the actual hero, Rika. Another interesting thing about it is the reversal of the usual optimistic-Hero and cynical-Lancer. Rika behaves cheerfully, but is secretly very cynical and has all but resigned herself to die. Keiichi, after a number of screw-ups caused by not trusting his friends, is optimistic and tells Rika that it is possible to beat the crap out of fate. He's arguably Rika's savior.
Rika even says something to a similar effect:
"There have been two worlds in the last hundred years where you never transferred here. Those were sad, dead-end worlds."
You could probably make a stronger argument for Hibari as the Lancer of the team. When he's actually ON the team, at least. He's extremely self-serving, unlike Tsuna who tends to get roped into helping others.
Rei is this to Kenshiro in Fist of the North Star. Originally looking to kill Ken, Rei eventually becomes Ken's closest ally and greatest friend, fighting alongside him and helping him restore some hope to the Crapsack World they live in. Turns out someone was just trying to smear Ken's name through the mud anyway. Upon Rei's death at Raoh's hand, Kenshiro called Rei "one of the greatest men that I have ever known."
Lancer/Yellow, from Robotech's "The New Generation" (aka Genesis Climber MOSPEADA), despite sharing the trope name, is a curious case, as he's less of a traditional Lancer and more of a mix of The Chick (uses his girly, "softer" looks and crossdresses to get the upper hand) and The Smart Guy (is level-headed and sneaky, as well as an Ace Pilot). Arguably, it's Rand/Ray and Rook/Houquet who take turns filling in as Scott/Stick's proper lancer.
Judai of Yu-Gi-Oh! GX has two Lancers in the earlier seasons — Sho, as the inseparable best friend, and Manjoume as The Rival, always trying to outshine him or be The Hero himself.
Rei Miyamoto is the lancer to Takashi Komuro in High School Of The Dead. Bonus points for being a member of the school's lancing club.
Asuka from Neon Genesis Evangelion likes to set up Shinji as her Lancer when in truth, she is the Lancer to him. While Asuka had formal training and has tons of self-confidence, Shinji has more natural talent and he eventually surpasses her in terms of synch ratio. Shinji always gets extra help from his mother's soul when he's in trouble. Asuka only gets the same once, right before her death. Jealousy towards the hero? Triple check.
Rebuild of Evangelion played this straight: Asuka not only acknowledges that she can't do everything alone, she's also the one who takes a bullet for the team and nearly dies in the process.
In Hunter × Hunter, Killuah fills this role perfectly. He even becomes aware of it himself.
Slayers has both Gourry and Zelgadis vouch between the Lancer and The Big Guy roles depending on the situation. However, though Lina met Gourry first, Gourry is an aggressive and incredibly dumb swordsman, and Zelgadis is far more intelligent and tactile, thus Zelgadis is more or less this trope.
Legend of Galactic Heroes: Siegfried Kircheis to Reinhard von Lohengramm, being the latter's best friend and moral compass. On the Alliance side, Walter von Schönkopf plays this role to reluctant hero Yang Wenli, often pointing out inconsistencies in the latter's moral and political outlook.
Blue Comet SPT Layzner gives us David Rutherford, who after getting over his bitterness over how The Hero Eiji Asuka wasn't able to save his friend Juno, becomes Eiji's fighting partner and one of his closest friends.