Answer:
I'm going to have to go with double displacement. Sue me if I'm wrong.
Explanation:
Synthesis? No. There would have to be one product, not two.
Decomposition? No. There would have to be one reactant, not two.
Single displacement? No. There are two elements/compounds that are switching places.
Double displacement? Highly likely. From the reactants' side to the products' side, nitrate and iodine switch places.
Neutralization? Uh, I don't think so. I can't remember why, though.
Combustion? No. O₂ would have to be one of the reactants.
<em>Lead nitrate + potassium iodide(?) ==> lead iodide(?) + potassium nitrate</em>
