My favorite grilled cheese is either my whole wheat olatmeal bread or Jewish rye (with caraway seeds) inside spread with Dijon mustard, then lots of Comte cheese (it's similar to Gruyere, but from the French side of the Alps). Butter the outsides and grill in my sandwich press. Sometimes with a slice of ripe tomato, or a couple of strips of crisp bacon, but not always.
Lately tho, I've been making a different one with soft, fresh Crescenza cheese, and the same breads, but dip the sandwich in a herbed, egg batter and fry in a pan on both sides until crisp and golden brown. Serve with homemade Tomato Soup!