Honestly, almost everything. I like most food better as left overs. Especially if it’s hot/spicy. It tends to get spicier overnight. Also marinara based foods do really well, like lasagna, manicotti, spaghetti, et cetera.
My favorite has to be our way of doing taco meat. A bunch of diced tomatoes (normally canned, sometimes fresh), and diced chili peppers, like jalapeños, poblanos, hatch chilis, habaneros, et cetera, spices and ground beef. Lightly fry the corn tortillas and eat. But I always make enough to have the next day, because after it’s sat overnight, it’s so much better.
Probably should have mentioned I use the air fryer to reheat most things. I have a microwave, but it doesn’t get a lot of use anymore. I don’t actually have a proper range/oven anymore.