bell peppers are S-tier. the crunch of putting the green ones on raw is undeniable, and the ability to balance the fennel in Italian sausage is incredible. the added bit of sweetness that comes from roasting the red ones and putting them on is rivaled only by the saltiness of pepperoni. the easiest standard pizza (ie. ≤ 3 ingredients) has to be pepperoni, roasted/sauteed red bell peppers and caramelized red onion (also an S-tier topping). using this as a base, it is IMPOSSIBLE to fuck up, add whatever you want and it's still going to be amazing.
speaking of bell peppers and vegetables in general, a good rule of thumb: if it's green, put it on raw. if it's not green, saute/roast it first for maximum flavor.
Italian sausage is ok IN EXTREME MODERATION but is severely overrated. adding any more than "a little" will result in tasting nothing (NOTHING) but fennel seed. properly seasoned ground beef rivals Italian sausage on a pizza, you guys are kidding yourselves.
olives are also a great staple, salty with a flavor that complements any pizza.
anchovies are vastly underrated, you (BAN ME PLEASE)s are crazy.
mushrooms are, without a doubt, the worst pizza topping ever. they turn the texture of the cheese from "stretchy but firm" to "disgusting and semi-solid," like semen or something. remember: you can't spell "mushroom" without "mush."
roasted garlic is high-tier. the roasting takes away the bite that raw garlic has.
pineapple: also vastly underrated and the only reason pizza with barbecue sauce was ever invented. the sweetness of the pineapple balances out the saltiness of pepperoni and ham in a way nothing else can, and lends a wonderful complement to the spiciness of toppings such as jalapeño and crushed red pepper.
spinach is excellent and also very healthy!
basil, somehow not mentioned, always very delicious.
but obviously the most important thing is making sure the toppings complement each other. as a pizza aficionado, I've come to the conclusion that just about ANYTHING can be put on a pizza with the right support.
some good pizza topping combinations:
1. pepperoni/red onion/red bell pepper/grilled chicken/spinach/roasted garlic
2. pineapple/green onion/smoked alligator sausage/jalapeño
3. basil/black olives/artichoke hearts/shrimp