It's possible it's a common developmental stage but I'm choosing to think she's unique.
Catie's favorite way to show she loves me is to headbutt me. If I'm on the floor with her she'll race towards me and headbutt me on the forehead, or the belly, or the shoulder. If you're carrying her you may get a headbutt on the chin, usually followed by an affectionate, high pitched squeal. It's a stage I'm loving and I'll be sad when it ends.
Brad and I are picking up the habit so if you get a headbutt take it as a compliment.