In terms of sheer wonder, it was the box of fifty crumpled up $1 bills that my mom gave me when I was about 12. We were poor and she saved up for a long time to do that, and I felt like all things were possible! She even threw in a jellybean, and had me shake the box first and try to guess what it was.
Sentimentally, I’d have to say the $10 engagement ring that my guy gave me when he asked me to marry him. I suppose that wasn’t the real gift, though. :D
For most practical, I once received the three-shot Hepatitis B vaccine for Christmas. One less way I could possibly die!