The fear of infinity.
Since childhood I’ve been haunted by thoughts of infinity. In bad dreams, or when feverish or migrainish, I’ve been tormented with endless thought loops that often make me vomit. As a little kid, hallucinating from a high fever, I scared my mom by yelling, “Tell everyone to stop running around counting to a thousand!” (At the time, this was the largest number I knew of.) Outside of these circumstances, that is in daily life, I find infinity to be just another incomprehensible and therefore mildly spooky notion, kind of like the Holy Trinity or how much money Gates really has. Still, I can feel the potential for screaming terrors if I delve too deeply in thoughts of unendingness.
It’s a good thing apeirophobia doesn't impact my day-to-day life, because reading this ad for treatment gave me a cold shiver: “The Infinity Fear Clinic at The CTRN Phobia Clinic is entirely results-focused, so we charge you for the result you want: freedom from infinity fear - regardless of how long it takes.” Aiee!!! (Italics mine.)
The CTRN Phobia Clinic: http://www.changethatsrightnow.com/
They have a highly entertaining list of fears (including Fear of Japanese Culture--!!), and all the text is automated, producing the silly sentence quoted above.
The Phobia List: http://www.phobialist.com/
Arachibutyrophobia: Fear of peanut butter sticking to the roof of the mouth.