Lasagna/manicotti/stuffed shells. YES. If I make lasagna for dinner one night, I wake up in a good mood the next day just thinking about leftovers.
Pulled pork. Just gets better, especially if it's sauced.
Spiral ham. Cook for a couple of hours, eat for a week.
Meatloaf. I prefer this the next day--pan-warmed slices of meatloaf on a roll with a little mayo and mustard are heaven. Heaven, I tell you.
Chili. My idea of the ideal make-ahead meal. Even resurrected from the freezer, it's delicious.