What's the hottest Christmas gift for kids this year?

I don't have any children of my own but I have a niece and nephew that I love to spoil. My sister not very helpful when I ask her what they want for Christmas. So needless to say I am out of loop on what the hottest toys are this season. My niece is 9 and my nephew is 2. Any help or suggestions would go a long way in making me look like the "good" uncle.