I agree about onions being great on pizzas. But I always like pepperoni topping the veggies. Even a generous amount of parsley is good on pizza if pepperoni is on top to flavor it. I tear the pepperoni slices up to make them go further and to blend in better with the other toppings. Since the outer edge of the crust gets done fastest, I add more moisture via sauce, cheese, veggies, and pepperoni to the outer edge to the extent some runs off onto the seasoned pan and still cooks up nice.
Definately the pepperoni has to be top.
Other hams than pepperoni can be as useful though.