My childhood favorite was peanut butter (crunchy) and dill pickles on wheat.
I also like sharp cheddar and tomato on rye, toasted. Not exciting but absolutely the thing, with a bowl of tomato soup, for a cold day.
I like Reubens but made with brown mustard istead of Thousand Island.
My mother, who is from New Jersey, grew up on cream-cheese and grape jelly.
My dad once packed himself a peanut butter and liverwurst, but forgot to take it to work so my mother gave it to me for lunch (I don't recommend this combination, however).