Scarr - Objectively he best slice of pizza in the city, he even mills his own flour in the basement.  (Long live the king.)

Di Farra - A close second, the original Di Farra is still making these himself with the help of his son. This place is in the middle of nowhere, there's no other reason to go here, and you'll still wait an hour in line. And it'll be worth it.

Prince St - Not a traditional slice, but the spicy pepperoni square is amazing

F&F - Just opened last year, but it's very well done, and the crust is especially good. The sausage and sage pie is the best slice of sausage on this list. The peperoni is also solid

Rizzo's - The thinnest, most crispy crust. A lot of people like their plain slice, and while good, the ricotta and sausage is objectively better. Also get garlic knots.

Patsy's - The original Patsy's, and the only coal oven slice in Manhattan or Brooklyn. It's only $1.75, and turnover is so high that it'll always be fresh out of the oven.

New Park - It's by JFK, and it's still on this list, that says something. Also a fantastic coal slice.

Baby Luc's - Mostly included in deference to it's older sibling, Lucali.  Lucali is probably the best pie you can get in the city.  Luc's has the same quality, and lets you get it by the slice.  The only mark against it is that it's grandma style slices, which while good, I just don't like as much as traditional NY style.  

Joe's - the platonic ideal of a New York slice.

Best Pizza - It must be, or else they couldn't call it that.  But seriously, the place to go in North Brooklyn.