I make a super easy one with leftovers from a large roasted chicken (or turkey).
I dice up the leftover meat, then defrost a small package of frozen mixed vegetables. I drain the veggies, then mix them with meat and a jar of Heinz gravy (chicken gravy for chicken pie, obviously).
I pour the mixture in a large casserole dish and top it with a package of refrigerated biscuits (just open and separate biscuits, then space them evenly around the top of the casserole).
I bake it at 350 degrees until the biscuits are browned (about 20 minutes).