While How I Met Your Mother is about a group of friends, that doesn't mean there are no fights between them. Over the course of the show, most of the gang fall out with at least one person - whether that is an argument in a couple, someone battling it out with a secondary character, or two friends getting into a screaming match.
These fights aren't always the healthiest, of course, and there are definitely moments where arguments crop up over silly things - but these are the ones that had a huge impact on the show, or on the relationships themselves.
Ted & Stella Fight Over Where To Live
When Ted and Stella were dating, he spent most of his time with her and her daughter in New Jersey, but somehow believed that once they got more serious, she would end up moving to Manhattan to live with him. Unsurprisingly, she's not ok with that, as it would mean uprooting her life and her daughter to have less space, and they end up having a fairly big argument over what their future would look like.
This really should have been the moment that Ted and Stella realized they weren't meant to be - and it was later echoed in their fight over inviting exes to the wedding. That fight, of course, also ended the relationship, as Stella left Ted at the altar for her ex.
Robin Cuts Her Father Out
Robin and her father have always had a strained relationship, for obvious reasons. Her father is extremely strict and harsh with her, and doesn't really show her any affection or love. However, she still wants to be a part of his life, and to impress him, up until the moment that she finds out that he got married without even telling her. Furious that he would be so uncaring, she ends up cutting him out of her life, and refusing to invite him to her own wedding. They do make up, eventually, but this is probably the biggest parent/child split on the show.
When Marshall Refuses To Fight
The best-known physical fight in the series is also connected to one of the biggest emotional fall-outs. When Ted, Barney, and Doug get into a fight with a couple of guys at the bar (although technically Doug does all of the fighting), Marshall is the butt of jokes for not joining in.
So, angry at his friends for making fun of him, he ends up lying to them about the severity of the charges that are laid against them for the event. While this argument may pale in comparison to the fight itself, it's big for Marshall - especially as he is usually so kind and easygoing.
Ted & Zoey's Whole Relationship
From the moment they first meet, Ted and Zoey seem to be fighting. As a result, it's difficult to narrow things down to just one fight over the course of their relationship. They fight about the Arcadian, of course, but that's not all. They fight at Thanksgiving, leaving to Zoey kicking them out of her apartment. They fight as friends, they fight as enemies, and they fight as a couple. Their entire relationship is essentially one big fight, which makes it one of the most memorable in the show.
Lily & Marshall's Mother
Although Lily is a lovely person, she doesn't always get along with Marshall's family. They find her snobby at times, and she cannot understand a lot of their traditions - all of which comes to a head at Marshall's father's funeral, when his mother starts yelling at Lily about everything she does. This fight isn't a terrible one, though. Lily actually realizes that by giving Marshall's mother someone to take her feelings out on, she's helping her get through the day - something that she thanks Lily for later.
Robin & Barney Get Divorced
Although it only comes in at the end of the series, when the gang's futures are being laid out for the fans, Robin and Barney's big fight is one that changes everything. In flash-forward, they are married, but seen fighting in a hotel room. Barney is angry at Robin for always being busy with work, Robin is angry that Barney isn't happy whether he stays in New York or comes with her on work trips, and their relationship breaks down. It's the fight that ends in their decision to get divorced, and it's absolutely heartbreaking.
The Bagpipes Fight
This is actually two fights, in the episode 'Bagpipes'. One is between Lily and Marshall, who are fighting over Marshall's refusal to do the dishes (and the terrible way that he phrases it to Lily), and the other is between Robin and Barney, who are pretending to be the perfect couple while constantly fighting in private.
The fact that this fight takes up an entire episode, and involves almost everyone in the group, is why it is clearly a heavy hitter.
When Ted Calls Lily A Grinch
When Lily returns to New York from San Francisco, she and Marshall are eventually able to reconcile, but are still living apart - and Ted is still angry. He pretends not to be, but Lily finds an old answering machine message from him calling her a "grinch" (the show's fun way of bleeping out a swear word during a Christmas episode), it all comes out. She's angry at him for calling her that, he's angry at her for abandoning him and not apologizing, and it all blows up. Lily steals all the Christmas decorations, and Ted ends up going to spend Christmas with his cousins... until thankfully, it all blows over in the end.
Marshall & Lily Fight Over The Future
Toward the end of the series, Marshall and Lily hit their biggest fight - and it's one that they can't seem to 'pause' (a trick that they use to stop fights getting in the way of their lives). Marshall has been offered a position as a judge, but Lily has been offered a position in Rome in her new art career, and both are determined that their job should come first. This fight isn't just huge, it's painfully accurate, as they bring up old grievances, battle it out, and Lily ends up leaving - albeit temporarily. In the end, fans know that Lily and Marshall reconcile, but it was shocking to see just how big their fight could get, despite how much they love each other.
Ted And Barney Stop Speaking
Ted and Barney are (almost) best friends throughout the series, but they did have one major argument that nearly ended the friendship completely, when Barney slept with Robin. Barney came clean to Ted, but he was furious, and punched Barney in the groin before cutting him off completely - and it was only after Barney was hit by a bus that Ted realized he did still care about his friend. This was not only one of the biggest fights in the series, but one of the most frustrating, too. Ted was angry about Barney breaking the 'bro code', that bans men from sleeping with a friend's ex, but Robin and Barney were both single adults at the time, and Ted's fury was an overreaction - especially as he didn't cut Robin off.