I can't say that I fast forward, but the first scene immediately after the Sollozzo killing in which Michael is in Sicily, bores me.

The scenes in which I never miss are the horse's head with Woltz, the meeting in which Michael volunteers to kill Sollozzo & McCluskey, Santino's death, the sitdown with Five Families, and Vito & Michael talking about how Michael will be betrayed by a Corleone associate.