Well, firstly Eclipse is my most favourite one and then I'd say Twilight AND Breaking Dawn :), equal competition amongst them.
Anyway, there are more than one fave parts in each book. So, firstly, I love the tent scene and also the one where Edward proposes Bella, in Eclipse. And then, I like the one where Bella feels her first jealous feeling when she comes to know about the thingy Tanya once had for Edward ( lol, I lmao when Edward says Bella's cute when she's jealous :D). It was even interesting to know about Jasper's past finally, and the best thing would be the battle at the end. I'd love to see the battle version from the movie ASAP. As I already mentioned, Eclipse being my most fave one, I like almost everything in the book except when Jacob kisses Bella against her wishes :x.
As for Twilight, I enjoyed it much after reading it from Edward's perspective, i.e, Midnight Sun, though it was only for the first 12 chaps ( I swear I downloaded that draft from SMeyer's site and I do wish she starts writing the book soon ). The blood typing scene is good too and I don't have words to describe about the meadow scene. With such a huge imagination, that would be best imagined :D
And then coming to Breaking Dawn, firstly, the way Bella describes the wedding processes and all was really good ( fact is I'm not very acquainted with American weddings and reading it from the novel gave a lot of insight for me into them). And then I liked how Edward takes care of Bella in every possible way, made me wish I find my Edward soon too, lol! I also loved every part where Renesmee was involved, and then Bella's shield and how she lowered it to let Edward read her mind was just awesome! Finally, I think the 'blonde jokes' between Jacob and Rosalie were pretty funny, hehe :D. Come to think of it, I really liked the book a lot. I keep reading my fave parts again and again whenever I find time :).
Lastly, I didn't like New Moon much, and the reason is simple - I hated that Edward left Bella, though he thought it was for her own good :x. But I enjoyed the reunion scene and the one where Aro gets frustated when he gets to realize that Bella is 'immune' to his power as well ( I guess that one's better shown in the movie version, though it must be natural for Aro to get frustated in the book as well). Reading New Moon, didn't really make me like Jacob, let alone change me into Team Jacob. Team Edward forever though!
Finally, I'm a hard core fan of the Twilight series and I'm proud to say so :)
I say my favorite book would b Breaking Dawn, but lyk any other twilight fan, i hav a favorite part in every book :P
From Twilight: When Bella and Edward r in the meadow n when Bella's heart starts racin every time Edward tries to touch her in the hospital
From New Moon: When Bella has her epiphany n realizes that Edward luvs her
From Eclipse: The tent part n when Bella agrees to hav a wedding
From Breaking Dawn: The wedding, when Jacob throws the metal bowl (that says 'fido') at Rosalie's head, when Bella beats Emmet at arm wrestlin and shows Nessie how shiny she is, when Bella realizes that Jacob will always c her as the normal,human Bella n when Bella shows Edward her thoughts
From Midnight Sun: When Edward finally realizes that he luvs Bella n when Edward could read the Ms.Cope's n heard her sayin "he's too young for me, too young, too young"....or at least sumthin along those lines XD
from twilight its the 'spidermonkey' part, always makes me smile
from new moon its when bella goes to stop edward from walking out into the sunlight in italy
from eclipse its the tent
from breaking dawn its the honeymoon