Hate to be pedantic, but had to go with 'onion' because it's the only one on the list which actually is a vegetable. All of the others are fruits, with the exception of mushrooms which aren't even plants at all.
cucumber is definitely my fave. i can literally just snack on them this part is not in order of favor: tomatoes are also very good. I only like mushrooms cooked onion is great as it adds great flavor to dishes just recently started liking olives, but they are really tasty eggplant is ok especially in a good dish peppers are ok orange are the best of the bell peppers. i love the flavor of a good jalapeño and pablano