If you're talking sandwiches, I've been trying to "fancy up" my standard turkey and cheese. So I went for whole wheat tortilla, spread with a bit of cream cheese, some chives or green onions, a slice or two of turkey, and some sliced avocado. Roll up (if it all fits) and enjoy! Sometimes I also add dried cranberries. Yum.
Salads are good too if you add lots of yummy stuff to the lettuce. Cut up sausage, chicken, or some cooked ground turkey, chickpeas, wild rice, various nuts and/or seeds, feta or goat cheese crumbles, dried fruit or a cut up canned pear... All of those make great ingredients for salad.
If you have access to a microwave, of course your choices become much more broad, and mostly in the leftover area. I love leftovers! Last year I was really smart and, before each long stint of work, I took a day or two to make a variety of casseroles and other meals (ziti, tuna noodle, chicken tetrazzini, meatloaf, bean soup, chili) and then freeze them. It was great to have them available to just shove in the oven (if I remembered to thaw them) when I got home from work. And then of course I had the leftovers for lunches for a while.