was it the tune during Prime's narration? The "autobots" woot.
I seriously loved the score. IMO Jablonsky did a good job of capturing and differentiating the autobot and decepticon elements in the score.
EDIT: when watching the film the 1st time, the tune "arrival to earth" played when Sam and Mikaela watch the heavens awaiting the autobots, actually gave me that congested feeling before you burst into tears (how do you call it?) lol.
I guess it brought back memories and now that I'm older, I actually get to see the childhood heroes play it up again (this time though in a present context w/c is cool).