Really hard challenge because I am always in the search for the next book so while I do, in fact, re-read some of my books I never actually read them more than twice so my selection is limited.
Angelfall by Susan Ee, I have read this book at least 5 times since I bought it.
Blood of Eden series by Julie Kagawa, I have read the two books in this projected trilogy from cover to cover at least three times, it is an awesome series in my humble opinion.
Once Burned by Jeaniene Frost, I initially hated this book and found Vlad an overbearing asshole but it grew on me and I ended up loving it and reading it at least 4 times.
Bared to you by Sylvia Day, what can I say, I liked the plot, I like the character and I find the sex hot. I've read it like 5 times or more and the next two books in series I have read at least three times.
Obsidian and Onyx by Jennifer L. Armentrout, I initially really loved this series and like book 1 and 2 but it has since declined for me, maybe my taste grew or series stagnated, I dunno.
Now after these books things get dicey because my liking are ever changing and I own and buy so many books that some of them get lost in my bookshelves until I re-discover them again.