For my daughter, I am most excited for her to open her American Girl doll. She has no clue about it and does not expect it at all since she just got the McKenna doll in December (she earned it so we had to order it before the end of the year). I got in on that great Today Show deal where they had two dolls featured for $50 each. I picked up Marie-Grace for her. So excited as it was totally spur of the moment. It makes me giddy to think about her opening it.
She has asked for a DSi to replace the one she had that broke so she's getting one of those too and she'll be thrilled, but I think the doll will make a bigger impact.
For my son... he has asked for an iPod touch so we picked up one for him. I know he'll be excited about that, but I really think what will thrill him even more is the World of Warcraft mega blocks sets that I picked up last minute (huge discount on Amazon so I couldn't resist!). He is 7 so while he'll love the iPod, the mega blocks sets will be a bigger 'wow' as far as something to play with on Christmas Day.
I'm bummed I don't have anything for DH that I feel that way about. He kinda knows about all of his gifts and he is really hard to shop for this year. When I ask what he wants he says he wants to pay off bills. So, for his 'big' Christmas present we're paying off another credit card. LOL Works for me though.