What is the most disturbing thing someone has ever admitted to you?

Divorced female colleague to me one lunch time: I am wondering if you are wanting to explore being special friends because you seem to be especially kind to me and I've been wondering about what you really think for a long time.

Reply in my head: NO WAY!

Reply out loud, kind, but firm explanation that she had completely misinterpreted what she had seen. We continued to work together amicably but it took me a while to get over the surprise/shock.