What’s something offensive someone has asked you? How did you react?

A few years ago before my grandmother passed away, she asked me, "So... when are you going to give me a grandchild?"  I responded by saying, "Wouldn't you rather I give you a grand daughter-in-law first?"   That totally shut her up, as she wasn't expecting that answer.

I don't even have a beer or food gut, or have ever been pregnant  

...but one time this lady I sort of knew had it her head that I was pregnant for some reason and asked me about it. I turned around and solemnly told her that I lost the baby just weeks ago. The look of horror on her face omg.  

I was probably an àss for going that far, but I like to ensure that for the next person they will think twice before opening their mouth again.