Oh, there are a bunch of single tracks that I'll whistle after playing a game for a while. I'll never forget that one bit of boss music, that sad theme, and let's not forget the triumphant music at the apex of you awesomeness in that one game. Okami, Legend of Zelda, Final Fantasy, Oblivion, the list goes on and on and goddam on.
And yet, in my mind, it doesn't get better than Chrono Cross. Ye flipping gods I love the music from that game. From the trailer cinematic playing "Scars of Time", all the way to the invocation of the titular Chrono Cross, triggering "Life - Faraway Promise", a glorious piece that starts simple and beautiful, then swells into a full orchestral score that touches my soul in a way that very, very few things in this world can.
It. Is. Magnificent.