Finney: public speaking, he just hates it
Robin: he's actually extremely afraid of spiders but would never admit it
Bruce: snakes, but he would suck it up if you were also afraid
Vance: he would never admit it, but he's kind of afraid of dogs
Billy/paperboy: throwing up. It's honestly his biggest concern
Griffin: death. That's why he does all these escape plans and is the escape artist