A phobia is an intense, persistent fear of a specific object or situation that is out of proportion to the real danger and often leads people to avoid what they fear. Beyond familiar examples such as heights or spiders, clinicians and case reports also describe rarer specific phobias.
Examples of unusual phobias include trypophobia (repulsion or fear of repetitive patterns of holes), globophobia (fear of balloons, often of the popping sound), arachibutyrophobia (fear of peanut butter sticking to the roof of the mouth), omphalophobia (fear of belly buttons), and phobophobia (fear of fear itself or of developing a phobia). Whether a fear counts as a clinical specific phobia depends on diagnostic criteria such as persistence and impairment, not on how common the trigger is.
Source: Live Science — 10 unusual phobias that actually exist