Lizzie and Jane. It's funny because their personalities are very different, but they get along and have a very powerful friendship. Lizzie would do anything for Jane, and Jane is always there for Lizzie when she's feeling sad. I almost envy their relationship because if I had a sister, I would love for her to be like Jane Bennet.
A second favorite is obviously the Darcy siblings, William and Gigi. They are literally polar opposites in personality, yet Darcy would do anything for his sister, and Gigi would do anything for Darcy. Sometimes I wonder if I would be different if I had a sibling closer to my age . . .