Mockingjay

In Mockingjay, we learn that Katniss acts on impulse and the things she does are selfless. She goes through many deaths in her life and always finds a way to avenge it. Katniss does all this impulsively. She doesn't value feelings, but she values survival. But to herself, she's not the top priority. It's the people around her like her family, her friends, and the members of her community.

One example would be when Katniss becomes the Mockingjay in exchange for the immunity of her loved ones. At first, she refuses to take that position in the rebellion, but later, she sees how everyone scorns the tributes that were captured by the Capitol. Katniss fears that they'll only be freed from there, to come to District 13 and be tortured. So she becomes the Mockingjay by convincing President Coin into her terms and conditions. This shows that Katniss does things for others, even if it means taking a risk.

Another example would be when she unexpectedly shoots and kills President Coin instead of President Snow. She was supposed to do the honors of killing Snow, because of his inhuman crimes against Panem. But she aimed her arrow at Coin because Coin took away the one thing she loved from the start. Her little sister, Prim. President Coin sent Prim to the Capitol warzone to help nurse people, when a bomb exploded there. The bomb killed many children including Prim. If you read the whole trilogy, you can see that the main reason Katniss does all the things she does is for her sister. Prim was originally supposed to be in the Hunger Games, but Katniss volunteered in her place to protect her. So now, since Coin killed Prim, Katniss takes her anger out and shoots her. But she doesn't know why at first. Here again returning to the fact that she acts impulsively. Katniss always takes risks for her loved ones.

So everytime Katniss does something, like even sharing goat cheese, she's doing it for the sake of others. This is why she's so great. She won't go down without a fight. Katniss always listens to her heart before her mind.