From COB I would choose Kissing the Shadows because of the wild sweeps, Children of Bodom (Malmsteen influences and awesome intro riff) and of course the ultimate song for me "Children of Decadence" with the great picking part that starts at 3.30.
Sinergy: Definately, I spit on your grave and Suicide by my Side.
I think that only the last Sinergy album reaches technically COB