From day one there's all manner of Ship Tease going on between Kim and Ron. Certain exchanges ("If she saw us coming out of a date movie together, she might, you know..." "You. And me. On a date?" "Not that we, y'know, would or anything...") and certain scenes (the parody of the famous upside-down kiss) littered various episodes, and "Emotion Sickness" was one big tease from start to finish, while simultaneously teasing Drakken and Shego. The first episode has Ron declare "And contrary to popular belief, I am not dating Kim Possible" in what could be the quickest series-start-to-ship-tease since Mulder and Scully. All of which inevitably lead to their Relationship Upgrade at the end of season three.
"Homecoming Upset" had its fair share of Ron/Bonnie teases.
In the case of unresolved ship tease, Nigel/Numbuh One and Rachel/Numbuh 362. The season 5 finale showed them as very close friends, with Nigel constantly trying to snap her out of her Heroic BSOD. Then came "Operation: G.I.R.L.F.R.I.E.N.D.", which has them on a First Name Basis and did everything short of waving a flag in your face saying "SHE'S MADLY IN LOVE WITH HIM!"
In Justice League Bruce Timm admitted to doing this with Batman and Wonder Woman after shippers misintepreted a gesture of thanks as flirting in "The Brave and the Bold". Anybody who's familiar with the DCAU (specifically Batman Beyond) knows that Batman is going to end up bitter and alone...
The Backyardigans: Plenty of ship tease, but what crossed the final line was the song "I Need a Hand" during "Caveman's Best Friend". It's the end of the song, folks. When they're holding hands. Doesn't that scream "LOVE" to you?! I guess it does.
The DuckTales episode "Duck to the Future" was pretty Ship tease-y in the Magica/Scrooge department, what with Magica embracing Scrooge when the two escape from the Hindenburg...and reaching down his shirt for his Number One Dime.
Spongebob Squarepants: The promos for the 10th anniversary special "Truth Or Square" all focused on a scene where Spongebob and Sandy get married. In the actual episode it turns out it's all part of a play. Fan reaction has not been too hostile (albeit it was disappointing for some), which is good because it would look really foolish considering it wasn't a Ship Sinking.
While Fillmore! was mostly a No Hugging, No Kissing series, the writers definitely gave a Toy Ship vibe between the two leading characters. Mostly because their dialogue had a tendency to sound flirtatious at times, coupled with all the subtext of a Buddy Cop Show.
The special "Wishology" seems to finally lean the show in the Timmy/Trixie direction (and at the same time, gives the Timmy/Tootie shippers reason to be very sad), but at the end, the Reset Button returns Trixie to her normal self.
Phineas/Isabella gets teased a lot. Isabella spends the whole episode "Out to Launch" trying to ask Phineas to a dance... only to have him misunderstand her and invite Ferb along as a third wheel. In "That Sinking Feeling" Phineas and Ferb attempt to help Baljeet impress a girl, and Phineas later invites Isabella along, but not in the way you'd think. In "One Good Scare Ought to Do It", Phineas not only spends the whole episode trying to help her, but holds her hand practically through the entire song. Many smaller examples also exist.
Isabella spends the whole of "The Chronicles of Meap" trying to get registered by Phineas's "Cute Tracker", to no effect. Then Phineas explains he already took her cuteness into account and set the device to ignore her from the start. When he resets it to stop ignoring her, it immediately shorts out.
In The Movie, Phineas seems rather pleased when Isabella kisses him, and makes like he's going to do/say something else, but never gets the chance.
The episode "Vanessessary Roughness" does this for Ferb/Vanessa, especially given the cheek-kiss at the end.
The hour-long special "Summer Belongs To You" teased two of the three most prominent pairings in the show: Phineas/Isabella and Ferb/Vanessa (andBuford/Baljeet, ofallthings). It didn't tease Candace/Jeremy however, considering they became an Official Couple at the end of the special.
"Phineas and Ferb's Quantumn Boogaloo" almost confirms the ship, while at the same time opening a new can of worms. While 20 years in the future Isabella is ecstatic to hear Candace's kids comment she looks like their Aunt Isabella, proving she must marry Phineas. Then past!Candace points out she could also marry Ferb and still be their aunt, prompting a look of shock from Isabella - and a point and a wink from the usually-stoic Ferb.
For some reason, despite the species difference, the show loves teasing Doofenshmirtz and Perry.
Scooby-Doo is infamous for possibly the longest ever (still ongoing!!) never-resolved Will They or Won't They? between Fred and Daphne (if you're not counting the live action movies). In Scooby-Doo! Mystery Incorporated Fred proposes to Daphne, and while that didn't work out Episode 51 had Fred come right out and say he loves Daphne followed by a Big Damn Kiss. However, after the jump to a different timeline, it's unclear if Fred's intentions were still valid at that point.
Even The Magic School Bus, which was primarily an Edutainment Show and aimed at little kids, managed to sneak in some hints between most of the kids. The most consistently teased pairings were the three cases of Opposites Attract: Ralphie/Keesha, Carlos/Dorothy Ann, and Arnold/Wanda. Arnold was a veritable Chick Magnet; he was also teased with Phoebe ("The Busasaurus") and Dorothy Ann ("Cracks a Yolk"), and a girl in another class named Tiffany ("Wet All Over"). One episode teased him with both Phoebe and Wanda at once ("Goes Cellular").
On Jimmy Two-Shoes, Jimmy comes into Heloise's room when the rest of the town is in hibernation. After trying to wake her up normally, he looks into the book she's holding, reading that a princess was awakened by a kiss. He looks at Heloise for a moment, who has sparkles over her... then tosses the book aside, muttering, "You can't believe everything you read." Another episode focusing on Hiccup Hijinks had a doctor suggesting that Jimmy cure Heloise's hiccups with a slight obstruction of the air passage, such as a prolonged kiss. Jimmy reluctantly decides to provide it, but in the ensuing hilarity, Heloise ends up kissing Beezy instead.
A season 4 episode of KaBlam! featured Henry falling in love with a one-shot character, Dawn. June was mad. So were the H/J Shippers. Did the creators forget about episode 29? (Oh wait, never mind. They did.)
During season 2 (Total Drama Action) the writers loved to tease Duncan with girls other than his canon love interest Courtney. Mostly this was with Gwen but he also ended up kissing Heather (as part of a challenge) and going on a 'date' with Lindsay (to deliberately infuriate Courtney). Then season three, the tease with Gwen became the truth.
Adventures of the Galaxy Rangers had quite a bit of this between Shane and Niko, especially if Chris Rowley was writing. "Scarecrow" is positively loaded. There's one scene where Shane was dancing with a local girl. Niko asks him later about his "girlfriend," and he remarks "She already has a date...and so do I." Then, there's the scene where Scarecrow busts into an injured Niko's room and attacks her. Shane breaks in and brawls Scarecrow, but is knocked against a wall. Before the Scarecrow can kill him, Niko grabs her BFG and shoots, scaring the thing off. As she swoons from the injuries she already has, Shane catches her, and says softly. "Easy, babe, sleep now." It was rather amusing when Rowley discovered the Fan Fic fifteen years later...
Hey Arnold! does this with some of the lesser characters: Harold with both Rhonda and Patty, Sid and Rhonda (in the episode "Wheezin' Ed"), Sheena and Eugene. Phoebe and Gerald also count earlier on, but they're more or less the official Beta Couple by season 4.
Used on several occasions with Odd and Sissi, who share an almost Slap-Slap-Kiss dynamic.
Odd gets a lot of Ship Tease with Aelita, calling her "Princess" and mentioning how pretty she is on more than one occasion. Aelita also seems to worry about him more often, usuually running to help him every time he gets hurt in Lyoko, and prefers riding on the Overboard with him. And then there's their kiss in season 4. According to Word of God, though, nothing comes of it.
Depending on the episode, Gadget was either interested in Chip, interested in Dale, interested in someone else (usually a oneshot character like Sparky), not interested in anyone, or unaware of the concept of romance.
One-shot teases like Dale and Foxglove, which carried over into the brief comic revival by Boom!. To a lesser degree there's Tammy and Chip, although this was rather one-sided on Tammy's part.
In ThunderCats, Cheetara is teased with both Lion-O (they spend an episode psychically linked, he's been shoved into her, and she has a throwaway line in the pilot about how handsome he'd become) and Tygra, who she eventually gets together with in the tie-in comics.
In "Song of the Petalars", Lion-O had a moment holding hands with Cheetara as she comforts him during a moment of grief... promptly killed by Snarf's glomping his face.
In "Journey to the Tower of Omens", Lion-O is a bit nervous over Cheetara's Hands-On Approach towards coaching him in the Sword of Omens' use, (which Wilykit notices, and merrily mocks with smooching noises) while Tygra later gapes over Cheetara's Super Speed, to which a smirking Panthro quips:
In "Rainbow Falls", there are a few moments that look like Fluttershy is flirting with Bulk Biceps of all ponies.
"Hearts and Hooves Day" is essentially an extended Ship Tease between Big Macintosh and Cheerilee. The two of them spend most of the episode under the effects of a Love Potion, but when they come out of, it's left thoroughly ambiguous whether there are real romantic feelings between them or whether they were just trolling the CMC. The two are seen walking together in a later episode, and in "Filli Vanilli", Cheerilee swoons at Big Mac's singing (though it isn't actually Big Mac singing; he is just lip synching).
In Twilights Kingdom Part 1, a few of Fluttershy and Discord's moments show them being very close, plus the passing mention of the two having a get-together for tea. When confronting Tirek, Discord tells him he's only capturing him for Fluttershy's sake. He also has a photo of him and Fluttershy together.
If you look closely at the captured Mane 5 after Discord is drained, you can see Spike holding Rarity.
Near the end, Discord gives Celestia a bouquet of flowers and winks at her. It does seem like a possible acknowledgement of the fan idea that the two of them had a thing once.
The Discord/Fluttershy tease is still going strong - Discord softly apologizes to her, and she forgives him. And then there's this little exchange:
Fluttershy:(to Twilight, on her Heroic Sacrifice) We're not worth it! Discord: Oh, but you are, Fluttershy. You're the pony who taught me that Friendship is Magic. I had magic and friendship, and now, I don't have either.
Intentionally or not, "What Was Missing" is seen as one colossal tease for Bubblegum/Marceline, the pinnacle of which was either A) a song that hinted at some incredible emotional pain in their past relationship with all the subtlety of a mountain, or B) that Bubblegum's stolen treasure was a shirt Marceline gave her (directly paralleling Finn's stolen treasure; a wad of Bubblegum's hair). The publically released storyboard reveals that originally there were even more hints planned.
"Sky Witch", holy crap. The episode literally opens with Bubblegum sensually sniffing the shirt Marceline gave her, and the end reveals that said shirt has more emotional significance attached to it than Hambo (Marceline's stuffed animal, the only thing she has to remember her Parental Substitute after he became the Ice King).
"Go With Me" is odd in that it seems to be both teasing and sinking Finn/Marceline at once—the whole episode makes a point of showing how they get along better than either does with Bubblegum, but Marceline pointedly turns Finn down when he seems to be asking her on a date. When it turns out to be Not a Date she goes, and they bond over their hatred of romance in the most romantically platonic way possible.
"Hot to the Touch" is dedicated to nothing other than teasing Finn and the Flame Princess.
And "Burning Low" caused a veritable explosion in the Finn/FP shippers, what with Jake calling Bubblegum out as being jealous that Finn likes FP, and the huge kiss and heroic rescue at the end.
"Gotcha!" teases Lumpy Space Princess/Finn, oddly enough, with the episode revolving around LSP trying to charm Finn and Jake only to fall for Finn's kindness and sincerity ("His hot lumps are on the inside!"). Near the end, LSP even admits that she thinks Finn is "hot".
Ever since "You Made Me" aired, fans have shipped Lemongrab with his clone. In what can only be described as something straddling the line between a Ship Tease and full-blown Word of Gay, Adventure Time writer Thomas Herpich once drew a picture of the Lemongrabs smiling and hugging each other... while butt naked◊. And in "All Your Fault," the Lemongrabs actually have children together.
"Too Old" refloats the Finn/Bubblegum ship to tease it briefly, only for Bubblegum to harshly shut down Finn towards the end of the episode, followed by Finn seemingly learning for the final time that the age difference between the two make them incompatible.
"The Pajama War" seems to have brought back the Finn/Bubblegum ship. The episode revolves around the two going on a kind-of-date, spending quality time together after the Candy people shove them in the closet to have "heavenly thoughts." The two have a few heart-to-hearts, play around with a giant cat and take selfies, all culminating in the two watching a sunset (on a screen) and admitting that they enjoy hanging out together, complete with them gazing at each other with sparkling eyes. The episode ends with Finn looking fondly at the pictures of him and PB having fun and being touchy-feely on his phone. All this happens after PB admits out loud that she wants to spend time with Finn, and she doesn't even leave when her people need her, instead continuing to do something for her own wants; chilling with Finn.
In Cartman Finds Love, Cartman obsessively ships Token/Nichole, since they're both black, and when he hears that Nichole likes Kyle, he tells her that he and Kyle are in a relationship, so therefore she can't date him. She then procedes to get together with Token. Kyle, in the mean time, learns about Cartman's rumor about the two of them and demands he tell the truth, but Cartman convinces him to keep quiet so he won't ruin Nichole's happy relationship. Nichole, however, dumps Token when she fears they're only dating because they're both black, and once Cartman learns Kyle is taking Nichole to a basketball game, he follows them, gets on the megatron, proclaims his love for Kyle (complete with singing him a love ballad and calling him "babe") in front of thousands. Kyle, who was an unwilling participant in Cartman's plan since he did really like Nichole, storms out angrily.
In the Gravity Falls episode "Summerween", Candy Chiu hanging on to Dipper after the Trickster's threat was enough to send some shippers into fits of squeeing. There were already Candy/Dipper shippers before, but this was the first remotely shippy real interaction they could grasp.
The episode "Northwest Mansion Noir" was full of Dipper/Pacifica (known as Dipifica by the fandom) teases.
Archer has unimaginable amounts of everyone on everyone but in the season 4 episodes, the most prominent is Archer and Lana, who have plunged into the Will They or Won't They? category. They used to date but since Archer's an unrepentant asshole, Lana has no desire to be in a relationship with him. However, they've slept together at least once since the break up and Archer shows signs of actually caring about her while she flip-flops between hating his guts and realizing he isn't a total Jerk Ass. This is taken further in Archer: Vice. Along with comforting her several times whenever things got too dire, Archer has tried his damndest to be the father figure he feels Lana's unborn child is going to need.
Lots of this in Teenage Mutant Ninja Turtles (2012). The writers use Donnie's crush on April as comic relief, but some fans are taking it seriously. Despite this, the writers do include some ship tease for Casey and April. On top of that, Leonardo has a variance of Dating Catwoman with Karai. They seek each other out for fun, they both care about the other's well being despite technically being enemies, and their battles absolutely reek of sexual tension.