Depends on the scar and the foundation. If you want makeup that will cover pretty much anything, try the theatrical stuff--Ben Nye, Mehron, etc. Foundation/concealer is easier to get a natural look with and you can get it anywhere with a cosmetics section. Unless your scar is very dark, I'd recommend just using regular civilian products.
ULTROS [Final Fantasy VI] (30%)
Haydee Tebelin (manga) [Gankutsuou] (10%)