I've read and watched a lot of series, so the ones below are the ones that have left a lasting impression on me. I'm not very good with words though, but I'll try to mostly keep it spoiler-free.
I love Haikyuu a very normal amount. I've watched the anime and read the manga a total of like 5 times by now. The characters all feel so real and the character arcs are all so satisfying. This series got someone who hates physical activity to consider moving LOL.
I actually found out about it through a MAD on NicoNicoDouga in like 2013 lmao. One of the first shounen that actually left a lasting impression on me. I love the unique setting it sets itself in and the world buidling.
I don't normally like love triangles, but this was really well done and did not stress me out.
This manhwa is such a journey omg. The character growth of the fl is so well done and I loved the storyline.