Simon Lane makes his feelings about spiders quite clear, and squeals in hysterical fear whenever one appears in a game he and Lewis Brindley are playing. He'll quickly get over it, until another one ambushes him.
Carlos Vittery of The Magnus Archives is terrified of spiders, though his phobia is unusual – he has no problem with pictures or videos of spiders or even spider horror films, but seeing an actual spider, or knowing it's there, absolutely terrifies him.
Lauchlan of Mix Beer With Liquor lost an eye in childhood, and has developed a crippling fear of becoming blind, or having his vision impaired in any fashion.
Like Ace Ventura and his bat phobia, animal enthusiast Catee Wayne (of "Boxxy" fame) has an inexplicable loathing of geese. The geese episode of "Weird, Gross and Beautiful" is delivered in a flat deadpan with zero interest in the subject matter.
"Sigh. They're really extra-good at nommin' on grass because their beaks are, like, extra-pointy or something. All the better to bite your small children."
Carol Burke, Allen Birkman, and Sierra Manning of Survival of the Fittest v4 all suffer from aquaphobia. In Carol's and Allen's cases, they actually first woke up on the island near the beach, causing them to freak out.
Lucahjin has a practically crippling fear of water and drowning, despite being perky and plucky the rest of the time.
Ironically, Neptune from RWBY is terrified of water that's even just a few feet deep.
MMORPG Game Masters
After getting his avatar banned because of Real Money Trade, Arthéon can't get anywhere near a Game Master and refuses to call for one when it would the appropriate thing to do.
While Simon Minter (miniminter) isn't exactly scared of tuna per se, he has an extreme dislike for it. So naturally, the rest of the Ultimate Sidemen used this to their advantage and took the time to shove a can of the stuff under his nose during his patience test. He almost cried.
Who Back When host jD absolutely hates moving plants and plant monsters. He admits in the 100th episode that he cannot watch certain Doctor Who series with When Trees Attack type monsters, such as "The Seeds of Death" and had a hell of a time reviewing the Big Finish Doctor Who audio book "Hothouse."
Flying (aviophobia) or Heights (acrophobia)
Pizza Face from The Grossery Gang is crippled by his fear of heights, which he learns he has during a mountain expedition. It was first an internal fear that he wasn't recognizing, but when he fully becomes aware of it, he's in such fear that he somehow goes naked from it.