One of the most powerful bits in the book comes very near the beginning (Jonathan is only starting to realise that there is something strange about the Count) when Dracula gives a truly epic speech about the history of his race. In a different context, the speech's content would be worthy of a particularly good Rousing Speech. This is sadly (though unsurprisingly) omitted from many film versions, though the Francis Ford Coppola version had Gary Oldman doing a heavily abridged version: "What devil or witch was ever so great as Attila, whose blood is in these veins?"
Jonathan escaping from the castle by scaling the wall.
Renfield trying to attack Dracula when the former realizes he's come to the house to feed on Mina.
Mina realizing she can use Dracula's Psychic Link against him and telling Van Helsing to hypnotize her so she can see into the Count's mind and locate him.
No one can forget Arthur Holmwood, after having been told By Van Helsing that staking Lucy would free her soul, doing it without any hesitation or wavering whatsoever.
A moment that's acknowledged in universe, when Jonathan climbs down from a tower twice, and goes down into Dracula's crypt again in an attempt to finish him off. Van Helsing and Dr Seward both remark how it must have taken a lot of nerve to do it.