Gnarls Barkley's "Crazy" is such a song. Cee-Lo Green could live to 100, recording a song a day, and he'll probably never match this one. It's that good.
And for me, it always comes down to the opening lines:
I remember when, I remember, I remember when I lost my mind
There was something so pleasant about that place.
The first time I heard this song was on our first family vacation to Hawaii, during the summer of 2006. What the heck (ok, I didn't say "heck") was that?, I think I may have asked.
The song of the summer of 2006, and quite possibly the song of the decade: "Crazy," by Gnarls Barkley.