I have at different times done many things listed:
Cook one big batch/make 5 meals on Sunday- I've done "Cafe Yum" bowls with brown rice, black or red beans, cheese, and salsa. Then the "cafe yum" tofu/almond/tangy sauce and some sour cream. I made the rice, packed them up, and brought the sour cream to work. I liked it for about 4 months, then got bored. I also did Tuna Nicoise sandwiches this way (making a second batch on Tuesday night. get/make some crusty bread, put tuna, green peppers, olives, boiled eggs, tomatoes, oil and vinegar on the sandwich, wrap it up tight, and eat the marinated sandwich. This lasted about 3 months. Pasta with tuna, pesto sauce, and peas or whatever vegetable lasted about 2 months. I've also sometimes done a hearty soup or chilli with crackers, but that's a one week at a time deal.
Dinner Leftovers- This is what I'm doing now. I got a free trial of Mealime and it sends recipes for 1 person for dinner and luch for the week along with the shopping list. I'm liking it. If you are already cooking 4+ nights a week it is no extra effort. I'm not much of a cook, but I'm really learning with this, though the food isn't super cheap.
Modular snacks - Hummus, yogurt, celery, baby carrots, an apple, a string cheese stick, sliced cheddar, crackers, some pasta, some lunch meat, pepperoni, boiled eggs, leftover grilled chicken. Buy a combination each week and leave at work. I particularly like Pepperoni, String (mozzerella) cheese, a tomato and some crackers for a pizza like flavor. THis doesn't get boring, but it doesn't feel like a "meal" sometimes.