Fear is important in our life. It helps us to not get harmed and is absolutely natural. Everybody knows someone who is afraid of spiders, flying or even space monkeys. Spiders can be poisonous, planes sometimes crash and space monkeys are basically killing machines, however here are the strangest, most irrational fears that I've found.
1. Papaphobia (Fear of Pope)
This phobia is triggered by an emotional trauma just like many other specific phobias. It's related to Hierophobia, which is fear of sacred things and people. You may think that this fear is irrational, but I've heard that popes have laser eyes and their hats give them the ability to read minds! I don't know where I've heard that, but I did... I think.
2. Xanthophobia (Fear of colour yellow)
Xanthopobia is caused by a traumatic experience with a colour yellow, so the origins vary for every case. It may have been triggered by geting hit by a school bus, getting stung by a wasp or getting hit by a school bus full of wasp, driven by a banana. In China colour yellow was feared, because receiving a yellow scarf from an emperor meant was an order to commit suicide. People with Xanthophobia may be even afraid to pee sometimes.
3. Turophobia (Fear of Cheese)
People with turophobia avoid cheese mostly because of its "gooey appearance", but in some cases even the sound of the word "cheese" may cause a panic response. It's a shame if you are french and turophobic. (French stereotype joke). Why live if you can't eat pizza?
4. Trypophobia (Fear of Holes)
It causes panic and anxiety in people who see irregular patterns of small holes like the ones shown below:
So this people may also be afraid of cheese, but only if it has holes in it. How amusing :P
The only hole I'm afraid of is the one in my heart.
5. Sesquipedalophobia (Fear of Long words)
Sesquipedalophobia - The most ironic phobia. You are afraid of long words so you can't even say the name of your condition. Someone has a twisted sense of humor. People think that this phobia is linked to lack of education, which causes people to feel anxious when confronted with a long word, because they are afraid that they might mispronounce this word.
Follow me 
and you'll be immortal!
(Maybe... I don't promise anything)
Sources:
Phobia wiki
Common-phobias
Phobia wiki
Wikipedia
Phobiasource