If you work downtown, I highly recommend checking out Pittsburgh Poke. This place doesn't appeal to the eye on the outside, but the food is delicious. I usually get a create-your-own bowl, which consists of rice, 2 meats/fish, endless toppings and fantastic sauces.
It's a little pricier than your typical on the go type spot, but given the amount of fresh quality food that you get with your order, it's totally worth it.