Sure, here are some anime that have a small number of episodes and are still popular among fans:

{Death Note} (2006): 37 episodes. A high school student discovers a notebook that allows him to kill anyone whose name he writes in it. He uses this power to try to create a perfect world, but soon finds himself caught up in a dangerous game of cat and mouse.
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Death Note anime
{Code Geass: Lelouch of the Rebellion} (2006-2007): 50 episodes. A young prince gains the power to control minds and leads a rebellion against an oppressive empire.
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Wikipedia
Code Geass: Lelouch of the Rebellion anime
{Attack on Titan} (2013-present): 49 episodes (season 4 still ongoing). Humanity is on the brink of extinction after being driven to the brink of extinction by giant humanoid creatures called Titans. The story follows a group of soldiers who fight to protect humanity's last remnants.
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Attack on Titan Wiki - Fandom
Attack on Titan anime
{Fullmetal Alchemist: Brotherhood} (2009-2010): 64 episodes. Two brothers, who use alchemy to search for the Philosopher's Stone, uncover a deeper conspiracy that puts their lives and the fate of the world at stake.
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Wikipedia
Fullmetal Alchemist: Brotherhood anime
{Violet Evergarden} (2018): 13 episodes. A young woman who was once a soldier is now a ghostwriter, helping people to express their feelings through letters.
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Violet Evergarden anime
{Made in Abyss} (2017-present): 13 episodes (season 2 still ongoing). A young girl named Riko sets out to explore the Abyss, a dangerous and mysterious cave system that is said to contain treasures beyond imagination.
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Made in Abyss anime
{Your Lie in April} (2014): 22 episodes. A young pianist who lost his ability to play after a traumatic event meets a violinist who helps him to rediscover his love for music.
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Your Lie in April anime
{The Promised Neverland} (2019): 12 episodes. A group of orphans discovers a dark secret about their idyllic orphanage and must find a way to escape from the sinister forces that control their lives.
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Promised Neverland anime
These are just a few suggestions, and there are many other great anime out there with a small number of episodes. I recommend checking out some reviews and trailers to see which ones you might like.
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