One I've tried is cucumber with tomato sauce. It didn't taste so bad.
I routinely make unusual pizzas. One style we like to go with:
A white pizza with 1) thinly sliced raw green beans, asparagus, or kale 2) leftover grilled dark meat chicken or sausage to add a smoky punch 3) then usually sundried tomatoes or artichoke hearts 4) garlic and black pepper