What are the "must have" Christmas gifts this year?

What are the "must have" Christmas gifts in your house? Every year, there is usually one gift that many parents go all out in finding their kids. I remember years ago, it was Elmo and then another year, it was Furby (I remember I looked online and in all the area stores the month before Christmas for those things for my stepkids trying to find them in stock).

My kids have various things on their lists this year. Some of them want guitars and cell phones. My son wants a Wii (he's dreaming). My stepson wants a guitar amp. My stepdaughter just has CD's and DVD's on her list that she gave us but my husband is supposed to talk to somebody at work about a used saxophone he had up for sale awhile back. She mentioned awhile ago that she wanted one (she plays clarinet now and can easily switch over). I'm hoping this guy has one in great shape for sale. That'd be perfect.

I have no idea what to get my four-year-old yet. She'll be easy enough I think - any toy commercial that comes on is a toy she wants.