A puppy, born Christmas Day 1998. She passed earlier this year. Easily the best gift I've ever received.
Worst? Probably any one of the like ten toy airplanes I got while I was growing up. Or any toy car. I would always go to play with my neighbor's Barbies instead.
Best: Mario Party (3 or 4, I can't remember), mostly because every Saturday for nearly 2 years straight I used to play it with my family. We rarely did family things before that and sadly we don't do much as a family know.