I've heard lots of writing advice about how it's a good idea to have the ending in mind before you begin writing. I don't always do that, but for my still-untitled Novel #4, I had a pretty good idea of where I wanted the story to end. Except while I was revising, another idea called to me, one that seemed more fitting for my character, and I tried it out.
So now I have two different endings. Both work, but in different ways. Have you ever had to decide between alternative endings for your story? How many times have you changed your ending?