I am a big cover person too. If the cover doesn't match the book I get very upset. I can't remember any I have read that hasn't matched the book. One cover that comes to mind tough are the Twilight books. I loved the cover with the black, red, and white flower, and the ribbon. But the blurb kept me from reading the book for a long time - I had no interest in reading about Vampires. I did finally listen to Twilight as an audio book and wondered what everyone was gushing about...it was no Harry Potter. Then a friend invited me to a free screening of New Moon - after drooling all over Jacob and the great story line I was hooked - and loved the series!
The other book that I thin of is the cover of "1,000 White Women" - I LOVED this book. What surprised me about the cover is that the book ends in a certain way...and if you look closely at the cover it gives it away - but subtly so you don't even realize it gives away the end until you have read the end! I loved that.
I tend to move away from science fiction looking covers, and half naked people (unless one is Taylor Lautner), or vapires for that matter. Covers are important draws for me.