Toradora! is basically all Crowning Moments separated by resolutions and buildups. The entire series actually sometimes manages to be a tearjerker, funny, and heartwarming AT THE SAME TIME during certain scenes.
Really the entire pool arc was a giant heartwarming moment after another...no scratch that their entire coexistence, while it may have been started out by ulterior motives, was heartwarming in how much they were willing to do for each other beyond what would be considered part of their agreement.
Also, Sumire's confession.
Taiga sends Sumire a letter which just consists of calling her an idiot. How is this heartwarming? It Makes Sense in Context and is related to the aforementioned confession.
The race at the end of the school festival.
The entire Christmas arc was heartwarming just seeing Taiga being so happy and content for once. The part where she sings to the school with Ami gives an impression of how far she's come going from being the bane of the student body to.....this.
Ryuuji surprising Taiga dressed up as a Santa Claus teddy bear at Christmas Eve in Episode 19. Unfortunately, this scene is soon followed by one of the show's saddest moments.
Taiga's delirious confession in Episode 21: "Please take these feelings away from me. Make me stronger. I'm no good right now. No matter what I do, I can't stop... loving Ryuuji."
When Taiga comes back from her absence after her injury on the ski trip, Ryuuji uses any excuse he can to make her stick around his place for a little while. And then he gets tears in his eyes when he realizes how important spending time with her really is to him.
Episode 24 has Ryuuji running away with Taiga to his grandparents' house. The Crowning Moment of Heartwarming comes when he introduces Taiga to them: he grabs her by the head, pushes her to his side and says "Also, this is my wife!". The blush in Taiga's face is priceless.
And last but not least, the True Love's Kiss scene, with Taiga in pajamas and wearing a white sheet like a veil of sorts, tippy-toeing her way to Ryuuji's lips in the Grand Finale.
Easily the final scene in the series when after over a year, Taiga and Ryuuji reunite. When Ryuuji confesses to her, she becomes flustered and headbutts Ryuuji. The look on Taiga's face when he confesses is unforgettable.
Way back in Episode 2 when Taiga tries confess to Yuusaku, what she actually does is all but shout her love for Ryuuji without using the words.
In a similar vein in Episode 2, Ryuuji's speech on Tiger and Dragon's counts as one as well.
The recently-released OVA based off an extra short story, "Ben-to no Gokui", is a mix of Crowning Moment of Heartwarming and Crowning Moment of Funny: To summarize, Kitamura's grandmother starts making boxed lunches (ben-to) for him as Ryuuji becomes envious and insecure of her talent in lunch-making (Played for Laughs, of course) and becomes overly determined to make a better lunch than her, starting from making grand lunches, to rice balls, to instant noodles until he is driven to COOK the rice INSIDE THE CLASSROOM. When everyone smells the cooked rice, his plan to create the better 'ben-to' is foiled... that is until Taiga meets him on the roof and gives him a lunch consisting of rice balls she made herself. She claims that she was only able to make those rice balls because Ryuuji taught her how to. Despite the rice balls tasting... a little worse than expected, Ryuuji realizes the true essence of making 'ben-to' or boxed lunches. As long as it was made with your sincerest feelings, it would be delicious to the receiver, no matter what sort of food you made; Kitamura's grandmother made those delicious lunches to suit Kitamura's tastes, and Ryuuji made food to suit Taiga's tastes. The OVA ends with some sort of cherry blossom viewing party with Ryuuji, Taiga, Minori, Kitamura, Ami, Haruta, Noto, Kihara, and Kashii. Taiga is revealed by Ami to have made boxed lunch enough for everyone and Ami and Kitamura make Taiga feed Ryuuji (like how lovers usually do it) using her chopsticks, much to Taiga and Ryuuji's embarrassment and to everyone else's amusement. D'AAAAAAAWWWWWWWW~!