Ok. Plot idea! Comment (say please!) if you'd like to use it, and I'll comment back and delete it so no one else steals your plot if I want to give it to you! Also, you have to give me credit!
Genre: Romance/ adventure
Main character: any gender
Plot: What if, when you fall in love, your heart (not your physical one; the mental/emotional one) merges with the other person's? Then, when one of you hurts the other, it cracks? And when you try to fix it, it grows back, sort of crooked but still whole? And when you stop loving the person, it breaks in half, and you each get half? And it takes forever to grow back the other half. Be careful who you give your heart to.
Ideas:Can be integrated with another plot; try and make it sad! I think it would be good if it ended the on a sad note, with the main character's heart being only half, ending with heartbreak? It would be your decision.