I'm pretty predictable when it comes to my meals that travel with me. Depending on the timing in relation to my workout for the day, it's a selection of some of the following (each meal packed in a Gladware or Ziplock container -- luuuuv those things!)
Chicken breast, grilled at home and sliced
or
Lean steak, grilled at home and sliced
with
Several cups of broccoli or green beans
and (if a carb meal)
One yam or sweetpotato; or a serving of brown rice or oats
Occasionally I'll make a tupperware meal of brown rice mixed with browned ground beef or turkey, whatever veggies are laying around chopped up, and spices.
Another one I like is a low carb tortilla stuffed with fresh spinach, ground beef or turkey (or even cubed grilled steak), mushrooms, and a little cheese.