Depends on the joint, some places I'll get the supreme, minus onions and mushrooms, others I'll go for pepperoni and sausage, some just pepperoni if I'm just keeping it simple, I also like ham and pineapple, depends on my mood.
Although on a semi-funny related note, when my girlfriend and I went to Italy we stopped and got pizza (of course) in a little mountain village in the north. To our surprise they had peperoni pizza, so we ordered it. Came with cheese and yellow peppers on it, that was it. It was still amazing pizza though, we loved it and actually got it again, but it turns out peperoni (one "P") is peppers in Italian. Had to say davioli (for spicy salami) if you wanted something more American.
Also thin crust, NY style is the way to go, thick crust pizza is disgusting. If I wanted some fucked up version of lasagna (I'm looking at you, Chicago) I'd order lasagna, that's not pizza.