Meatlovers.
I refuse to eat any pizza that has vegetables on it outside of the tomato sauce.
I used to be of this opinion, but I tried some spinach and ricotta pizza recently and it was absolutely lovely.
Only thing I didn't like were the tomatos with skins on top, since they're really difficult to cut in a single bite, so they end up getting slopped about as you eat, and make an annoying crunch.
But the spinach was lovely!
It makes a great base pizza for throwing meat on top of.
Edit: Oh, and I suppose I have always enjoyed Sweetcorn on pizza though. But it's not exactly very 'vegetabley'. It's like the sweetness of pineapple, without the juice.