6. Banana peppers
Pizza and pickle rarely collide, but banana peppers make a solid case for their continued marriage.
5. Sun-dried tomatoes
No other vegetable offers quite the burst of flavor as a sun-dried tomato. I consider it an "event topping" that slows down the eating process and forces you to enjoy each bite, rather than just setting your teeth to autopilot and mindlessly making a slice disappear.
Pizza shops typically divide their non-meat toppings into two distinct categories: plebeian veggies like bell peppers and more expensive glamour vegetables. In the case of artichoke, that extra dollar goes a long way. It isn't as powerful as most of the other vegetables on the list, its piquant nuance makes it more of a supporting player. If it could shoot the three, it would be the Steve Kerr of toppings.
This was almost rolled into the ham category, but they're truly different beasts. The curing process adds salt without the sickliness, a silky textural element, and kills the Easter Sunday aftertaste found in other hams. It also adds a distinct air of grown-up-ness to an otherwise childish food.