Lol yeah hardcore, but the black lung disease one is just so awesome cause it's looong, but then again, hippopotomonstrosesquippedaliophobia is just hilariously ironic. Btw, it's red underlined when you type it in.
Mississippi is an awesome word. But for something different, maybe butter or champion. Kind of hard to think of your favorite word, but those came to mind, i guess. O_o
This actually not a real phobia, but my favorite word is aibohphobia. Is is a joke phobia and supposedly means the fear of palindrome, being a palindrome itself.