What are some movies that end with an unanswered question?

I just saw The Heiress which is about an unappealing, plain rich women who is courted by a handsome but poor man. The question throughout the movie is whether he loves her or is just after her money. Surprisingly, this question is not really answered in a definitive manner at the end- leaving both possibilities to ponder. I was also surprised to find I liked this ending.

What are other movies like this? Thanks in advance.