I love all these stories! I couldn't agree more that seeing kids' reactions to cosplay are some of the most memorable and satisfying.
The only one for me that comes to mind though was at a recent convention. I was cosplaying as Sasuke Uchiha from Naruto Shippuden standing around talking with my friends when I felt something tugging on my pant leg. I look down to see a little girl cosplaying as Sakura with the biggest smile on her face. I waved and said, "Hey there Sakura". Her smile seemed to get bigger (if that's even possible lol) and she said, "Hi Sasuke! Can I have a hug?" Of course I said yes so I knelt down and opened my arms to give her a hug. She jumped into my arms and gave me a kiss on the cheek saying, "I hope you come back to the leaf village real soon" and ran off back to her parents. It was adorable lol
PAX Prime 2014:
Cortana - Halo 4/Forward Unto Dawn (0%)
Tifa Lockhart - FFVII (90%)
Gerudo Guard - Legend of Zelda: Ocarina of Time (10%)
Aki Con 2014:
Sakura Con 2015: