I have brown bagged it for 4 months straight now and rarely eat the same thing, unless it's something I get hooked on. I like both cold dishes and things I need to reheat, some stuff I buy prepared.
Salads, it's amazing how many different ways you can prepare fresh veggies. I usually skip the lettuce and use tomato, cucumber, onions, apples, grapes, broccoli, cabbage, celery, peas, cheese, lump crab, imitation crab, clams, anchovies etc. in various combinations. It's doesn't need to be fancy either, a fave is a sliced tomato topped with 1 oz lump crab, tbsp bleu cheese and sprayed with Wishbone's Ceasar Salad Spritzer. I can prepare it in a few minutes and it tastes great. The sky is the limit with salads. Oh yeah, real bacon bits are 25-30 cal per tbsp and make a tasty addtion to any salad.
Heat and Eat, same thing here, the sky is the limit. Frozen veggies are super easy to nuke and anything can be used to make it more interesting. A fave of mine is Birds Eye Stir Fry veggies, some chopped peanuts and sriracha sauce, quick easy good. I also eat lots of beans, anybody can make a pot of pinto beans interesting with an onion, can of Rotel and some diced pork.
Wraps, move over boring sandwich. What can't you put in a wrap? A fave of mine is imitation crab, onion, bleu cheese, jalapenos, sprouts and mayo. Put enough in a wrap and it's a one item lunch and it's easy since it requires no reheat.
Prepared foods and snacks. I keep it interesting by eating Tasty Bite's Indian and Thai pouch stuff, pour a pouch of curry or spicy potatoes over a bag of Tyson grilled chicken breast strips and your done. Yogurt, Del Monte fruit cups, nuts, jerky, fresh fruit.
Key for me is I mix and match and I shop for everything I need on Sun. It's nothing to grill a top sirloin or pack of boneless skinless chicken breasts on Sun and use it for a few days. If you pair it with a different veggie each day you have it made. Toss some sliced sirloin in with some fresh basil, onion, tomato and top it with chili paste, fish sauce and lime juice and bam you have a Thai salad.
A good place to get ideas is recipe sites like Allrecipes or Recipezaar.