Almost forgot this one, I'll add a fried egg or two to pretty much any leftovers to add something new, leftover pasta? Couldn't imagine having it without a fried egg. Leftover Indian food? Bitch please, you're crazy if you don't throw a fried egg in there. Also, fried egg + burger = delicious.
Speaking of burgers, the best upgrade to any burger I've ever tried is to press a quarter tab of butter into the center of the patty (assuming you're making them from scratch--which you should be). When you bite into the burger, you get this awesome buttery-spice pocket in the middle.
Ugh, I knew this would happen. I hate to be the guy to spark the debate that eventually ends in twenty messages being edited to "keep it to pm" but I can't just overlook this one. To say that ranch dressing is somehow an upgrade to pizza is to blaspheme on a level higher than Joe Rogan at a Tool concert wearing a Phish hoodie.