This is where I struggle a bit. I pretty much eat the same thing for lunch every single day, a salad with grilled chicken.
Sandwiches or wraps - for Paleo use romaine/lettuce instead of bread or Siete tortillas. I've heard Belgian endives can be used, but I've never tried them.
Leftovers from dinner the night before.
Make a dinner recipe on Sunday and portion it out for lunches.
Tuna fish salad