The animations that play on the onset of each route.
The game being able to pull off such delicate subjects without being insensitive at all.
Emi, despite losing her legs in a tragic car accident which claimed the life of her father, continued running using prosthetics, and is the best runner at the school, at that.
Also in Emi's route, who comes to the rescue when Hisao and Emi almost break up? It's someone whom you wouldn't expect... Misha! Shizune also deserves some credit for telling Misha to intervene. Quite the surprise, and if you take her advice, she'll be the key to getting back on the path to Emi's Good Ending.
Getting Emi's Good Ending via this path could be called a CMOA for Hisao. He knows exactly what will happen if he screws up: he'll lose Emi. He's under immense pressure to save what he and his girlfriend shared, and judging from the lack of narrations (other than pointing out Emi's reactions to his words), he doesn't even think about what words he's using. Yet he doesn't crack; he somehow keeps his cool throughout the whole thing. His speech to Emi about determination is the icing on the cake.
If you make a different choice at Emi's house, Rin gets her own by essentially forcing Hisao and Emi to face the issue by leaving them alone on the rooftop. Hisao notes afterwards that he must remember to thank her.
Deconstructed in Hisao throwing away Iwanako's letter, without even reading all of it. At first it seems like an awesome moment by itself, demonstrating Hisao's Character Development, but when you consider what the letter meant to Iwanako, and that the letter is a result of a Break the Cutie process for her, then it gets turned on its head. It's nice to see Hisao look forward to the future, but not necessarily when he unintentionally ends up hurting someone, especially a girl as painfully shy and fragile as Iwanako. Also, Hisao's act is meant to mirror Emi's tendency of running away from the more painful elements of her past by pretending they aren't there and always blazing full-speed ahead. The real Crowning Moment of Awesome is when he retrieves the letter and reads it completely, putting his bitterness behind him.
Shizune standing on top of the school, arms spread wide, fiercely and characteristically attacking Hisao's depression. She's such a badass. And the scene gets a huge boost from the art - Shizune's sprite, the background, the fireworks, and the rare camera movement.
The tour Hisao gives Misha of the school late in Shizune's route, recalling all the experiences he's had with her and Shizune, and urging her not to push Shizune away like he did with his old friends. It showcases his Character Development and is a crucial step in repairing Misha and Shizune's friendship.
When Hanako has a panic attack in class, Mutou and Shizune know exactly what to do and how to help her.
In a minor way, Hisao showing Hanako his chest scar, which no-one has seen since he left the hospital. He does it partly to prove to himself he can accept his past, and partly to show Hanako that she's not alone.
By her Good Ending, Hanako has managed to successfully open up by herself and even in her Bad Ending, as painful as it may be, she has the courage to tell Hisao that his pity makes her uncomfortable.
Hisao's Race for Your Love scene in Lilly's Good Ending. As heartwrenching as it is that Hisao has a heart attack mere meters away from her at the airport, the fact that he travelled so far just to say goodbye to her one last time is awesome in its own right. And what's more, it actually worked, convincing Lilly to stay with Hisao in Japan and giving the couple the happy ending they deserve.
By the end of Lilly's route, Hisao himself has managed to survive and recover from not one, but two major heart attacks. The man is nothing short of determined, to say the least.
Hanako gets one late in the route: she decides to join Naomi and Natsumi's newspaper group, and plans to travel to Kyoto with them. And she does this all on her own.
Crossing over with Heartwarming, after spending the majority of the route internally hating his circumstances, Hisao opens up to Rin about how much he resents being disabled. Rin's answer is to give him a hug and comment on his erratic heart rate. What happens next is a minor moment of awesome for someone who's had so much trouble getting his feelings out:
As of writing this, it has been several years since the game's final version was released, and yet you don't have to look far for either old fans who still hold fond memories or newer fans expressing how much they love the girls and their stories. Props must be given to 4Leaf Studios for making such a timeless game.
Not so much to do with anything within the game, but it has been mentioned that this is the first Visual Novel to end up on the front page of Game Faqs, placing 1st on the most wanted Faqs on the site before someone submitted a complete Faq. At its peak, it made the 3rd top rated PC game and 11th top rated game.
Within two weeks, the Katawa Shoujo thread has become the second largest thread on the Visual Novel section of the forum.