When I was a kid, my parents used to take my sister, brother, and I to K-Mart quite often. Those of you who are old enough to remember, K-Marts used to have a deli/ice cream stand, and they would sell these sacks of 5 ham sandwiches. It was just a few slices of their deli ham, some shredded lettuce, and mustard on a bun. My dad would always buy them and we would eat them in the car on the way home, along with the cola slurpee I would always get there too.
These days one of my current favorite sandwiches would be the veggie sandwich at Jimmy Johns. I get it on their whole wheat sliced bread, and add the hot peppers to it. It's got several slices of provolone, some kind of avocado spread, mayo, the hot peppers, lettuce, tomato, and it used to have bean sprouts till they took those off the menu. It's not a diet sandwich by any means, but so good.
Runner up would be the Grilled Chicken Philly sandwich from Mr. Hero. It's got sliced grilled chicken and bell peppers, on a hoagie roll with melted cheese on it. Surprisingly, it's relatively low in fat and calories. It only contains 7 grams of fat, so it's much better for you than say, a Big Mac.