The chase through the jungle!
Having only recently seen this film, I have to say, I was floored by the sequence in which Rainsford and Eve are pursued through the island by the dogs. It's just a pitch perfect action scene. The scene at the end where Rainsford fights Zaroff and his men back at the mansion is a close second (love when he breaks that guy's back!). Very kinetic and fast-paced.
And I got to say that I love that closeup of Zaroff's bug-eyed, insane expression with gnashed teeth when they're running through the tall grass (just before the waterfall scene). It perfectly hammers home just how singleminded he is, and really shows his utter madness. And when he shoots Rainsford and he (Rainsford) goes over the cliff, that insane little giggle Zaroff does is just great.
They couldn't make that chase scene any better if they tried!!!
Also, for any gun lovers out there, does anyone know what kind of rifle Zaroff uses?