What affectionate object that belongs to Mrs. Darling does Peter take with him when he leaves?
One of the things that the author talks of a great deal at the beginning of the story is Mrs. Darling's kisses, among other things.
Mrs. Darling is the consummate mother, wanting not just to love her own children, but unable to say no when, at the end, the lost boys come to their home looking for a place to live.
They all line up, with hope and trembling, to see if Mrs. Darling will have them. Without even asking Mr. Darling, she agrees to take all six of them. Mrs. Darling offers, too, to take Peter, but Peter is vehement: he does not want to grow up; how would he look in a beard?
Peter also wants to take Wendy so she can continue to take care of him, but Mrs. Darling won't allow it. She does offer to let Wendy visit him once a year to conduct spring cleaning on his home, and he agrees.
As Peter leaves, he takes one of Mrs. Darling's kisses as he flies out the window.