Does Anything in the Bible Make You Uneasy?

My mom and I were just discussing the pros and cons of Dispensational Theology (not a lot of pros were discussed!), and she brought up a particular passage that she thought was very important in relation to the end-times, and remarked that it was one that gives her pause whenever she ponders what it says.

I agreed with her about this passage in Scripture, and told her that of all things in the Bible, for me, it was probably the one that gives me reason to be a little bit uneasy as far as my eternal destiny is concerned.

I have heard R.C. Sproul say that this is perhaps the most terrifying passage in the whole Bible.

Can you guess what it is? And what are your thoughts about it?