Instead of microwaving your leftover cold pizza to make soggy hot pizza, try this: reheat the pizza slices in a large skillet on medium heat for 4-5 minutes, adding a domed lid for the pizza made with aluminium foil to help reflect heat back to the toppings without trapping steam inside.
Chef John from Culinary blog Foodwishes claims that the residual oil from the pizza crust in your skillet will be reheated and make the crust crispy again and by the time this happens the cheese will have melted again and warmed the toppings. He even says that he uses this method with delivery pizza to improve the crust.
Magic Pizza Reheat Method! [YouTube]