Magic Kingdom. It and myself have grown up together, being born the same time and place. It always takes me back in time when things weren't complicated and all my family was still around. I actually consider the MK a friend. Sounds cheesy, I know, but when so many important and lasting memories are tied up in a thing or place, you sometimes can't help but feel that way.
2nd place for me has to AK. While lacking a great attraction line up, the theme design and execution is tops. I really am transported to another world when I'm there.
I have to mention the EPCOT of the 80's. It was the most ambitious and utterly amazing thing I had ever seen. To this day, the memory blows me away. I really, really miss the "old" EPCOT.