How could you not love a bad boy love interest?! They are never actually bad, just misunderstood and broody :) Dean Holder in Hopeless is the ultimate love interest, for me. Also Mycroft in Every Breath by Ellie Marney (this is actually a mystery novel, but of course there is a romantic plot line) and Park in Eleanor & Park. Although Park probably doesn't count as a 'bad boy', he is just quiet. Perhaps it's actually introverted love interests that appeal to me, not bad boys.