I think the most fun I've had recently was against people who say "it's just a game" when they are winning if you complain about something, but when the table turns and they are on the losing side, they go cry so much about someone from their team.
A good example would be my last game, we were against a smurf Twitch jungle (fekker got 2 1v5 Pentakills in the game), and when I called him out on smurfing, his team, especially Sylas and Taliyah kept telling me to "shut up, it's just a game", and in Taliyah's case, she even said that "this isn't ranked, who cares about winning or losing". Later that game, we managed to win a few team fights and got some inhibs and would you guess it? Taliyah and Sylas themselves started spamming the chat with "report Twitch, throwing". The reason why we won those fights was because we managed to catch him out, and without him, they were useless.
We ended up losing the game as our Vlad went Rambo one too many times, and if you guessed it, Twitch got the "most honored" in his team after he got those 2 pentakills.
And I just can't help but laugh when people like these come up, and it's so amazing to turn the game around against them and see how their "chill, it's just a game, who cares about winning or losing" attitude changes faster than Zed mains saying "it takes skill to R - E - AA - Ignite".
(Note: If you're a Zed main and get offended, bad luck. I'll always throw dirt on the champ until he gets skill added back in his kit, as at the moment, it's harder to differentiate a good Zed from a bad Zed than it's to differentiate a good Garen from a bad one.)