Aside from what's already mentioned,
-Cottage cheese mixed with basil and tomato is one of my favorites (even better with crackers but good and low-carb this way).
-1 egg's worth of egg salad atop greens
-quick black bean salad with 1/2c black beans and some diced red onion, green pepper, cilantro, and lime juice
These aren't necessarily carb-free, but are not carb-dependent. Hope that helps.