Nizza Pizza was one of our favorite hang-outs when we lived in Arlington. Their pizza is pretty good (especially their stuffed pizza), but it's their subs and salads that got us hooked. Try their Italian Combo--mounds of meat, peppers, lettuce and olives with their signature house dressing on Italian bread--it's the best sub sandwich I've ever tasted, hands-down. Counting carbs? Well, their Antipasta salad is basically an Italian Combo with extra lettuce and no bread--and it's just as good.
The atmosphere is casual and friendly (you go often enough they'll know your names and ask about your kids)
One word of warning: It's best to avoid lunch hour during the school year
when the teenagers from the neighboring high school overrun the place.