In terms of filling calories, chicken breast meat is your best friend. It's actually terrible from a calorie/carbon standpoint, but I buy it at the local farmer's market to assuage my liberal guilt. One of my favorite lunches is a chicken reuben.
4 oz of chicken breast meat
as much sauerkraut (homemade) and fat-free thousand island dressing as you want
1 oz slice of swiss cheese (I use the real, 100% fat stuff, because otherwise what's the point?)
two slices of homemade rye IPA bread with whole wheat flour
Works out to about 600 calories, and I don't think I could eat more than one a day, it's so filling.
I make my own sushi/nigiri too, and I'll post on that as soon as I can take some pictures to show y'all up.