There seems to be an unspoken mandate these days at CBS, that their dramas set up a massive cliffhanger at the end of one season, to be resolved at the beginning of the next. Only shows that are in danger of cancellation (such as Blue Bloods, which has yet to pull a season-ending cliffhanger, and the later seasons of CSI NY) seem to be exempt from this silent directive.
Seventh Heaven: A few season finales have ended on cliffhangers, with the 7th season being the worst offender. Is Lucy pregnant? What happened that brought the head of the church and the police force to the Camdens' front door to talk to Eric immediately? Who did Mary elope with? Did Roxanne and Chandler get married? Of course, it was all resolved next season. Lucy wasn't pregnant, Simon got into a car accident that resulted in a young boy's death, Mary eloped with Carlos, and Roxanne and Chandler break up. Although we never did find out what happened to Christine or why Cecilia disappeared in early season 9…
24: Typically uses a cliffhanger at the end of each episode. The show also featured a season-ending cliffhanger in the final seconds of season 2, which, irritatingly enough, was subverted when the third season picked up three years later and the cliffhanger had already been resolved. This was later revisited in The Game, but it's annoying how the Season 2 and 7 plot arcs aren't fully explored at the end.
ALF: The final episode ended with the title character preparing to return to his home planet, only to have him and his host family surrounded by government agents. This cliffhanger would be resolved in The Movie, Project ALF.
Alias: Also a staple of J.J. Abrams' serial, as as acknowledged nod to The Perils of Pauline. Almost to the point of annoyance.
Season 2 of the new show ends, after having skipped a year, with a Cylon fleet appearing over New Caprica, the Battlestars and remnants of the civilian fleet jumping away, and President Baltar surrendering. The first episode of Season 3 skips ahead four and a half months, when the Cylon occupation is in full swing. By the fourth episode of the season, the Cylons have been kicked out and the search for Earth resumes.
The first season ends only moments after Commander Adama has been shot twice is the chest, right after initiating a military coup and arresting the President.
Big Wolf on Campus: In an unusual move, the second season of the light-hearted show ended with one of the main characters a stone statue after making a Heroic Sacrifice for his best friend. All the more dramatic because the show nearly didn't come back for a third season, but fortunately it was renewed and he was saved. An intentional cliffhanger, or at least the show wasn't unexpectedly cancelled.
Boy Meets World: Ends season 5 with one: Topanga proposes to Cory during their high school graduation ceremony.
Callan: An early British example was this TV spy series, whose second season ended with an episode where Callan was kidnapped and brainwashed into believing that Hunter, the head of his section, was an enemy agent. Callan kills Hunter and is himself shot; the episode and season ended with him mortally wounded and gasping to Meres, a fellow agent, "Toby, old man... I've been had!" The next season dealt with Callan's recovery and return to operations while being treated with extreme caution by his superiors.
An ill-fated attempt by NBC – in 1979, at a time when the network could not afford any failures – to popularize the concept of old-time movie serials into a weekly televisions series format. Three stories were featured each week, with each segment lasting about 15-20 minutes before reaching a "cliffhanger"-type conclusion and enticing the viewer to "stay tuned next week." This short lived '70s series was a homage to the old movie cliffhanger serials. The show had 3 different segments each hour, with each ending on a Cliff Hanger each week! (And just to rub it in, only one segment reached a proper conclusion before the series was cancelled!) The segments were as follows:
"Stop Susan Williams," inspired by the old "Perils of Pauline" serio-dramas of the 1930s. Here, the "Pauline" character is filled by model Susan Anton as the title character, a journalist who — while investigating her brother's murder discovers that the killing was part of an international conspiracy.
"The Secret Empire," a U.S. marshal who discovers a futuristic underground city. This installment was based on "The Phantom Empire" movie serial starring Gene Autry.
"The Curse of Dracula," about the famous Brams Stoker character taking the guise of a college professor, in an attempt to achieve mortality. Only "The Curse of Dracula" reached its conclusion within the 10-week run, as lack of viewer interest, poor reviews and ABC's powerhouse Happy Days and Laverne and Shirley, turned "Cliffhangers" into a show that truly left the viewer hanging after cancellation. As a postscript, the "Stop Susan Williams" and "The Secret Empire" installments were re-edited into two-hour "made-for-TV" movies for later re-airing by NBC, and included their intended conclusions.
The Colbys: The Season 2 finale (and Series Finale) had several cliffhangers, most of which were later resolved on parent show Dynasty, the most fantastic being Fallon's abduction by aliens in the California desert. Even for an over-the-top show like The Colbys, this was a Jumping the Shark moment.
Relied on a season ending Cliff Hanger every year. The most famous was "Who Shot JR?" in 1980, which lasted from March 21st to November 7th.
The 14th season finale, "Conundrum," also was billed as the series' finale of the original CBS version. However, the episode itself was not unlike the other season finales. Here, J.R. fears he has lost his empire and everyone that means everything to him, and contemplating suicide, is visited by an angel(?), who, in a It's a Wonderful Life-type dream, shows him how others would have fared without him. In the end, J.R. trains the gun at his head; Bobby, concerned for J.R.'s welfare, arrives at Southfork just in time to hear gunfire coming from J.R.'s bedroom, rushes to the door and says, "Oh my God!" Viewers are left to wonder whether J.R. killed himself ... a question that wouldn't be answered for another five years and the first of the reunion movies.
Desperate Housewives: The third season concluded with Edie Britt's apparent suicide after Carlos dumped her. The fourth season premiere revealed that she had actually faked her suicide in order to win Carlos back.
For most of its history consisted entirely of multi-episode serials, so obviously it's had a lot of cliffhangers. There have even been a couple of Literal Cliff Hangers.
Almost all of William Hartnell's stories were presented with a cliffhanger right at the end, except for season finales and one or two other exceptions, to create the impression of a single run-on adventure. This makes life notoriously awkward for Expanded Universe writers trying to find Time Skips to put stories in - Peter Purves once joked that there is "one scene change in "The Gunfighters"" that holds virtually all of his Steven & Dodo audios. (Of course, at the time, there was no concern about this sort of thing.) Most Troughton stories did not do this and there is a lot more room to add material into his timeline.
A particularly bizarre and interesting meta-example in the Classic series is at the end of "The Wheel in Space", in which Zoe has slipped aboard the TARDIS and the Doctor is worried about the idea of taking her with him. In order to demonstrate what she will have to face, he projects some of his memories onto the TARDIS's screen - "but edited together to make it into a story". What he shows is footage from "The Evil of the Daleks" - a story that was going to be repeated in the gap between seasons - and the cliffhanger is a closeup of Zoe's face as she stares at the screen in fear. This may be the only example ever of a cliffhanger that leads into a previous episode.
The modern series, which has multi-parters as a more occasional thing, makes it slightly easier to list.
"Bad Wolf" ends with the revelation that for the past century Earth has been controlled by the Daleks, and the Doctor promising he'll come rescue Rose from their clutches.
"Army of Ghosts" ends five million Cybermen arriving on Earth and seizing control, and the Void Sphere opening to reveal four Daleks.
"Utopia" finishes with the reveal that Professor Yana is actually the Master, as he steals the TARDIS, leaving the Doctor, Martha and Captain Jack about to be killed by zombie-esque hoards. The episode right after that, "The Sound of Drums" finishes with The Master aging and capturing the Doctor, imprisoning Jack, and Martha just escaping to witness the death of 10% of the Earth.
"Silence in the Library" ends with Donna disappearing mid-teleport with a scream, as the Doctor and River are cornered.
"Turn Left" finishes with Donna saving the day, and destroying an alternate universe where the Doctor died prematurely....but then tells him about the strange blond woman who said the words "Bad Wolf". At that moment, the old Arc Words from season one appear everywhere, and the cloister bell starts ringing.
The episode right after that ends with Daleks raging across the Earth, Sarah Jane being cornered by Daleks in her car, the members of Torchwood under attack, and the Doctor mid-regeneration.
"The Time of Angels" ends with the Doctor about to execute a plan to escape the Weeping Angels.
"The Pandorica Opens" finishes with Rory being mind-controlled and shooting Amy, the Doctor being locked inside an inescapable prison by all of his enemies, and the TARDIS blowing up with River inside it, destroying the entire universe.
The end of "The Impossible Astronaut" is Amy shooting the astronaut which killed the Doctor, only to reveal it to actually be a little girl. The next episode also has a cliffhanger, but one that isn't concluded for several more episodes, as it shows the same little girl regenerating in a back-alley.
The beginning of the new episode "The Impossible Planet" has a Shout-Out to the Cliff Hangers of the old series. In The Teaser, the Ood, who look like Lovecraftian horrors, walk toward the Doctor and Rose chanting "We must feed", and the close-ups and spinning camera angles match the old Who's Cliff Hangers perfectly. Naturally, after the titles, the Ood are shown to be perfectly nice and friendly, with their apparent viciousness being a Phlebotinum Breakdown: "We must feed..." — whacks the translation orb — "...you, if you are hungry. Do you want refreshments?"
Actually, the first episode of every season finale ends on a cliffhanger that is resolved by the following one. Usually in an awesome way.
EastEnders: "You aint my muvva!" "Yes I am!!" Dun Dun dundundundun....
Frasier: Even sitcoms aren't immune. Most of its season finales ended on a cliffhanger - the biggest one being the end of Season 7, where Niles and Daphne finally got together. Even the Grand Finale ended on a minor cliffhanger. The only seasons not to end with one were 1, 2, 3 and 6.
Friends: Ended almost all of it seasons with a cliffhanger, the most famous one being the season 4 finale, where Ross says the wrong name at his wedding.
Greys Anatomy: The fifth season ended with a cliffhanger. Either Izzie or George might be headed for the big OR in the sky. Or both.
Grimm: Had this happen for a mid season break, just after an old enemy had returned, his best friend had been hospitalized, and immediately after Nick has found out who has been having an (unwilling) affair with his girlfriend. They seemed to be aware of how this would make the fans feel, however. 2 seconds after "To Be Continued" showed up on the screen, it was followed by "...sorry"
House of Anubis: All episodes end in a cliffhanger to be resolved in the next episode.
How I Met Your Mother: The season 3 finale ended with Ted proposing to Stella (mind you, this was while Stella was hinted to be the title's Mother) and Barney realizing that he was in love with Robin. Stella said yes in the teaser of the fourth season premiere, and the rest of the episode took place several months after the teaser, partly because the season 3 finale had also featured Barney getting run over by a bus, which took him an entire summer's worth of physical therapy to heal from.
JAG: Had several cliffhangers. The first season ended with Harm being arrested for murder, though same episode was a Missing Episode and later adapted, thus bordering on Canon Discontinuity. The third season ended with Harm and Mac about to be shot down in a Russian jet while looking for Harm's father. The sixth ended with Harm lost at sea, having ejected from his F-14 trying to get back in time to catch Mac's wedding. The seventh ends with Bud stepping on a landmine while trying to prevent an Afghan boy from doing likewise. The eighth ended with Harm leaving JAG to save Mac and Webb against orders. The ninth ends with Webb apparently killed and the Admiral's retirement. The series itself ends with something like a cliffhanger, leaving the audience wondering if either Harm or Mac will retire after they decide to marry and whether they'll end up in London or San Diego afterwards.
Got in a really good one at the end of "Green With Evil Part 2". The episode ended with Goldar's sword apparently about to impale Jason's head.
Let's not forget Season 3's infamous cliffhanger with the villains' blowing up the Command Center, and leaving the Rangers pretty much screwed.note Until next season, that is...
Power Rangers Turbo ended with the mentors all captured or MIA, all powers and Ranger tech broken or destroyed, and four of the remaining five Rangers taking a space shuttle out to try and do something, lack of superpowers, FTL drive, and location of enemies be damned. The series actually ended on a "to be continued" just as the shuttle took off.
Misfits: Already taunting fans with severe British Brevity (i.e. the prospect of waiting a whole year for another six episodes), this show ended its first season on a horrible cliff-hanger: the main character was left buried alive, with no obvious means of escape.
Mission: Impossible: Used this constantly in Act Breaks (and, of course, in its two-part stories - the show's only three-parter, "The Falcon," even ended part one with Paris dangling over a cl... balcony!).
Season 4 Tony meeting his girlfriend's father, La Grenouille.
Season 5 Jenny's death and Vance separating the team.
Season 6 Ziva held captive by terrorists
Season 7 Paloma Alejandro and her gang walking into Jackson's store.
Season 9 Harper Dearing planting a bomb on the Navy Yard, which goes off with Gibbs, Abby, Ziva, Tony AND McGee all still inside. Ducky gets the news at Palmer's beachside wedding and promptly has a massive heart attacknote Not resolved yet, but the show is renewed, so it will be.
Psych: "Santabarbaratown", the season six finale did this with an excellent Bait and Switch: Psych's season finales are always Drama Bomb Finales, but so far have always had everything resolved by the end of the episode (although the Yin/Yang trilogy had some suspenseful Foreshadowing and changes to the status quo to entice the viewers). This time they seemed to be following the same formula: an extra-dark, extra-personal, extra-high-stakes mystery that was wrapped up by the end of the episode...but then a loose end appears at the very last moment, with Shawn and Henry both simultaneously realizing that Henry's old cop friend who is discussing the case with him at the beach was a corrupt cop just like Henry's other two old friends who had been exposed earlier in the episode. The old friend promptly guns down Henry for knowing too much, and Henry collapses, fate unknown and with Shawn still miles away at SBPD headquarters.
Has had bad luck with season cliffhangers: it's tried it twice, and both times immediately went on hiatus for years.
Season 6 ended with the lead characters apparently murdered by their evil future selves; the audience had to wait three years to find out how they got out of it.
Season 8 ended with the Red Dwarf being devoured by a genetically enhanced virus while most of the crew evacuates, and the main characters escape to a mirror universe. Except for Rimmer, apparently trapped on the disintegrating ship. The series ends with the screen saying "The End? The smeg it is!". This time the audience had to wait a full decade. And strictly speaking we still don't know what happened next, because the makers invoked an Un Installment and skipped forward to where everything was back to normal.
Episode 10, the midseason finale, ends with Monroe using the pendant to restore power to a fleet of attack helicopters and going after the heroes. Episode 11 picks up where the cliffhanger left off and resolves it.
The first season finale has one. Team Matheson makes it to the special room in level 12 of the Tower and successfully turns the power back on worldwide. But then Randall Flynn comes in, launches Intercontinental Ballistic Missiles at Philadelphia and Atlanta, and then he shoots himself in the head. Team Matheson now has to figure out what to do about those missiles before it's too late. Then you have the Monroe Republic led by Tom Neville trying to break into the room with intent to kill everyone in there, and Jason Neville doesn't look too happy about it. There's also the matter of the American government Randall is working for, led by the President of the United States, hiding out in Guantanamo Bay, Cuba, and now they intend to come back and retake what's theirs.
Sapphire And Steel: Each of the six "Assignments" consists of 4-8 episodes, with cliff hangers at the end of each episode except the last one.
The Sentinel: Season 3 ended with one of the main characters having been drowned in a fountain by an evil female Sentinel and a To Be Continued... at which point the show was cancelled. Fan outrage helped get it uncancelled for a half-season, long enough to resolve the storyline and come up with a less depressing finale.
The first season ended with the city of Atlantis on the verge of another wraith attack, Ford captured by the wraith, Colonel Everett surrounded by them, and Major Sheppard flying a booby-trapped puddle jumper on a suicide mission towards a Wraith Hive-ship.
The second season ended with several Wraith hive ships headed towards Earth.
The third season ended with the city stuck in the middle of empty space with limited air and a failed hyperdrive. Even if Jewel Staite was entering the show as Kaylee rather than Doctor Keller, it's a bit tricky to imagine them fixing it.
Season four ended with the slightly less impressive cliffhanger of an building collapsing on the team.
Stargate SG-1: Likewise, parent show ended almost all of its seasons with cliffhangers of varying magnitude, all with the ominous "To Be Continued..." caption.
Has had a Cliff Hanger in nearly every non-final season since Star Trek: The Next Generation's Season Three. It's no coincidence that that cliffhanger, "The Best of Both Worlds", is considered to be the best episode of the entire series (and good arguments are made that it's the best episode of the entire franchise. Edith Keeler might disagree, though...)
This one is particularly interesting in that it cleared the way for cliffhangers, previously a staple for soap operas, to be used in more "serious" TV shows.
At the time, this cliffhanger had particular punch because it was unknown whether Patrick Stewart would return for future seasons, and the episode ended with the very real possibility that his character was seconds from being killed. The writers left the second half open for this reason.
The Next Generation, Voyager and Enterprise always achieved their cliffhangers by splitting a two-part episode over the end of one season and the start of the next. Deep Space Nine had a rather more interesting approach however, in which the final episode of the season would have its own storyline wrapped up within the episode itself, but the next stage of the show's story arc was set up in the process.
Season One: Sam and Dean finally catch up with their father, John, only to find him possessed by Azazel, the Yellow-Eyed Demon. Sam catches up to them both and bundles them both into the Impala, intent on getting John (sporting a gunshot wound) and Dean (sporting the side-effects of outright torture) to the nearest hospital... when they're suddenly t-boned by a truck, leaving all three of them unconscious.
Season Three: Dean fails in his attempt to evade the Hellhounds and dies during the course of his last stand. The last shot of the season shows him screaming in abject agony... chained up in the depths of Hell.
Season Five: Despite throwing himself — and therefore Lucifer as well — into Hell with the Archangel Michael, Sam is seen standing across the street from Lisa's house, watching his brother enjoying a normal family life.
Season Six: Effectively double-crossing just about everyone, Castiel absorbs the thirty million souls of Purgatory and, fuelled by the immense power he suddenly wields, declares himself the new God, demanding that the world profess their love unto him, lest they be destroyed.
Season Seven: Crowley appears and abducts Kevin Tran (the Prophet/Word Keeper). The ensuing blast from the death of Dick Roman — the leader of the Leviathans — sends Castiel and Dean hurtling into Purgatory, leaving Sam alone on the mortal plane.
Season Eight: Dean talks Sam down from sacrificing himself to close the gates of Hell, only for Sam to suddenly collapse in some sort of agony. Meanwhile, Metatron takes Castiel's grace, rendering him human, and performs a ceremony that makes every single other angel fall from Heaven.
Third Watch: Had Cliff Hangers after its third, fourth and fifth seasons - the latter two both involving Bosco, Faith, Cruz, and a shooting.
Veronica Mars: Season One ends on several cliff hangers. Aaron Echolls has been arrested, but it's unclear how Veronica's relationship will be affected. The audience knows that Logan had an incident on the bridge where he contemplated suicide, although the characters don't.
Vintergatan: Had a cliffhanger Once an Episode, with no sign of stopping. Fortunately, the cliffhangers don't bother people that much. Why? Because it's always been presented that way, and there's danger around every corner in-canon, so it doesn't seem forced (and even when it does, it rarely becomes Narm — usually it's Narm Charm, and at worst, it's So Bad, It's Good) — and second, because that meant we got to hear the cliffhanger jingle.DAH, DADAH-DAH DAAAAAAH!
The first and fourth seasons end on extremely tense cliffhangers.
The second season doesn't, if you've been paying any sort of attention, but many viewers apparently missed the cues.
The funny thing about the second season finale is that it does have a cliffhanger, for the more minor plot of the coup in Haiti. The President's reelection, however, is a much larger arc and takes up much of the focus, so the subversion there is unexpected.
The X-Files: Used constantly. Three really annoying words: "To Be Continued..."
Sesame Street: The classic Ernie and Bert sketch featuring Ernie writing an "epic" story ... but it turns out to be the alphabet. Bert's enthusiasm (at least in the 1970s remake) quickly fades into irritation as he hears Ernie recite the alphabet, and give an over-the-top, overdramatic reading of the 'sad part" (letters H through P) and an over-enthused "action part" that represents Q through V. Bert really flips, however, when Ernie fails to finish the "big finish," leaving the story at "Y" and failing to reveal the obvious ending ("Z"). When Bert presses for Ernie to say the letter "Z" (without saying said letter), Ernie justifies failing to resolve this unresolved "cliffhanger" by suggesting that if he did, "then you'll never want to read it for yourself." Cue Ernie's trademark giggle and an annoyed sigh from Bert.
Soap: The final ep ended on four cliffhangers. It is yet unknown whether the South American guerilla militia firing squad Jessica ended the episode in front of were Bolivian.
Later, in an episode of the spin-off Benson Benson was visited by Jessica's ghost, leading many fans to believe that, yes, they were Bolivian.
The final episode of Benson also ended on an unresolved cliffhanger. Benson is running for Governor, while incumbant Governor Gatling is running for re-election as an Independent making for a three-way gubernatorial race. In the final scene, Benson and the Governor resolve their personal differences, then sit together watching the TV as a newscaster says, "And the Governor for the next four years is-"
Heroes: The de-facto series finale ended with Claire Bennett revealing her power to the world by jumping off the top of a ferris wheel and healing via news cameras; this was the beginning of the series' 6th Volume, Brave New World, which never came to fruition due to the show's cancellation by NBC in May 2010.
Farscape: Usually, fans become quite irate when cancellation leads to a series ending on a Cliff Hanger, but for some reason, when this show ended this way, the fans took this as a bold statement by the makers, refusing to give in to the Sci-Fi Channel's decision to cancel the show. Only a few people were annoyed that, given plenty of warning and knowing how unsatisfying such an ending would be, they didn't opt for a more graceful ending. On the up side, that season's main storylines were already resolved, with the last few minutes used to set up a new bit of drama for the cliffhanger. And we were eventually rewarded with a Grand Finale miniseries.
Plenty of warning? They'd already filmed the finale, and were working on pickups for other episodes when they found out. So much for a two-season pickup?
FlashForward (2009): The series finale, instigated after the show was canceled, ended with the second blackout happening 14 minutes after the future caught up, Bryce finally finding Keiko, Simon and Demetri stuck inside the NLAP mainframe, Olivia and Lloyd kinda/maybe/sorta/probably ending up together, Aaron managing to reunite with his daughter and revive her, Janis being wheeled unconsciously from the hospital by one of the Big Bad's henchmen and the almost certain death of Mark as the FBI building explodes. Adding to this a series of disjointed flashforwards from unknown characters, excluding Charlie's one of her in the future, gives us next to nothing solid to finish up the story properly.
Invasion: Partially avoided this by wrapping up most of the series's plots in the last couple of episode, but still managed to end on a minor cliffhanger.
Surface: Ended with the sea levels rising and the world now apparently dominated by monsters, with most of the issues raised in the series (such as who created the monsters and why) still unresolved.
Cleopatra 2525: Ended with three interconnected cliffhangers and two Reveals.
Joan of Arcadia: Was canceled in the episode where the series' Satan equivalent was introduced, gaining control of everything and everyone in Joan's life and poised to ruin it all.
John Doe: Another revelation 'hanger: What turned out to be its final episode revealed William Forsythe's character to be one of the bad guys.
Popular: We don't find out who Harrison chose, but more importantly the episode ends with Nicole gunning her car at Brooke, Brooke screaming as the headlights bear down on her, a fade to black, and the sound of sirens. Then the series wasn't renewed for the third season like TPTB said it would.
Odyssey 5: The 2002 sci-fi series ends with astronaut Angela Perry abducted by the AI's and scientist Kurt Mendel being arrested on suspicion of killing her. Plus the mysterious Cabal, which the team assume have something to do with the AI's and the impending destruction of the Earth, turn out to be a government force trying to stop the AI's and who believe that the Odyssey 5 team are the traitors.
10 Things I Hate About You: Had a pretty decent cliff hanger for the season one finale. Walter walked in on Kat and Patrick right after they finished having sex. Bianca and Dawn quit the cheerleading squad in protest over their friend Chastity being unfairly kicked off, only to find out that Chastity is transferring schools and they didn't have to quit. Bianca's boyfriend Joey had become a contestant on a reality show and she tunes in just in time to see him kissing another one of the contestants. Then the network decided not to renew the show and the season finale became an unresolved series finale. Though the series creator was nice enough to tell fans how things would have developed if the series had continued. Basically, Kat and Patrick's relationship would grow closer, though they'd eventually clash about college.(Kat wants to go and wants Patrick to go, Patrick doesn't think college is his thing.) We'd meet Patrick's mom and stepdad, and Walter would become a sort of father figure to Patrick. Kat's other possible love interest, Blank, would be around, but it wasn't quite going to turn into a full-fledged love triangle. Joey would get kicked off the reality show, causing him to lose a bit of his spark. His and Bianca's problems(from his cheating and bit of a personality change) would lead to Bianca confiding in Cameron, which would lead to a Bianca/Joey/Cameron love triangle. Chastity was going to be gone for good, since the actress quit the show, and Dawn would be given a bigger role to compensate.
Dark Angel: ended with a huge Cliff Hanger. The world just got aware of the Transgenics, who were claiming their own part of the town and got under siege by the police.
Primeval: The third series ended with Danny trapped in the Pliocene, Connor and Abby trapped in the Cretaceous, and Sarah coming up with an unknown idea to sort things out. And then ITV announced there wouldn't be a fourth series. There is talk of a movie, however.
It's been renewed for a fourth and fifth season, so looks like Connor and Abby will finally get out of that tree.
Hotel Babylon: Got Cut Short after four seasons due to low ratings but ended on a huge cliffhanger (unusual for the show that previously had few story arcs) after Sam finds out Juliet, his ex-wife whom he had been dating again, had aborted his baby years ago he struggles to decide if he wants to continue their relationship and work past it or begin a relationship with Emily who he had been getting close to. No ending was ever written.
Las Vegas: The final episode of the fifth season ended with Cooper's plane having crashed with him onboard, and Danny & Delinda changing their wedding to a memorial service for him. After the musician plays a sad song, Cooper suddenly appears at the back, clapping, and Delinda goes into labor. The End.
Sledgehammer: In the last episode of the first season, the title character accidentally triggers a nuclear explosion in the middle of the city. Da Chief can be heard screaming "Hammer!" as "To Be Continued Next Season?" appears on screen. The second season begins with a Hand Wave explanation that the following episode(s) occurs five years before the explosion (regardless of the fact that Sledge met his partner for the first time at the beginning of the series — but this could be explained if we assume that there was a five-year gap between the final two episodes of the first season).
A bit of a subversion, really, as the series was not expected to be renewed for a second season - which is precisely why creator Alan Spencer had the bomb go off in the first place!
Power Rangers RPM: Ends with a glowing red light coming from one of the morphers - the trademark of Venjix, the Big Bad. Looks like he survived by downloading himself into it... but RPM was the final season at the time of production. The series was later Un-Cancelled with Power Rangers Samurai and they did do a crossover with RPM, but acted as if it happened during RPM instead of after, thereby not giving any resolution.
iCarly: The last episode of the fourth season ended with Sam kissing Freddie, whilst Carly watched in the window.
V (2009): Ends with Diane murdering her mother, and her adopted child being able to give Humans Bliss.
Fast Lane: The season and, as it turned out, Series Finale had two major characters being taken over by Jay Mohr, and another jabbed with a potentially-fatal overdose of drugs.
Sherlock: Series 3: Moriary is broadcast on every TV in the UK. "Miss me?"
Mad Men: Season 5, ends with Don Draper being propositioned by a woman. The credits start before we can see if he really has decided to cheat on Megan. It's strongly suggested the Lady Killer In Love is gone and the philanderer is back.
Tower Prep: Just before the show was cancelled it ended on a big cliffhanger, where the students finally escaped from the school, just to find out that there is still much more to discover with the mystery.
Criminal Minds: Suspect Behavior: Followed the above-mentioned "silent mandate" from CBS concerning this trope by putting two of the leads in life-threatening danger, with another lead having to make the choice as to which one would die. Unfortunately, the show was a dud with CBS audiences despite the lead-in from its parent show, and the network decided to pull the plug after one season.
The final season of The L Word ended on an unresolved cliffhanger, of the viewers not knowing who killed Jenny Schector.
The final "Assignment" of Sapphire And Steel ended with the two title characters apparently trapped in a pocket universe with no means of escape.
The Sarah Connor Chronicles ended with a massive cliffhanger of John, John Henry and Weaver having been sent into the future, and Cameron possibly dead.
Starcrossed, canceled by the CW network, ends on a whopper, with Taylor possibly about to perish in a fiery car accident, and the signal from the Suvek having been received by a fleet of Atrian warships, which heads for Earth.