What scares you?

It's a simple question that all horror writers ask.  What scares people? For me it's a swarm of rats.  I think it goes back to when I ws a child and my parents took me to see Willard (the original) at the drive in theatre.  The scene where Willard takes revenge on his boss, played by Ernest Borgnine, stuck with me for many years.  Share what makes your skin crawl.