M14

The M14 is the default sniper you get when you start the game. It's a one-hit-kill, but only if it's a headshot. This gun is what you would most likely use when you start the game. It does good damage and has good distance. So if you're a fast aimer and have a trigger-finger, you'll get a good amount of kills. The only disadvantage is the ROF of 2 per second, but other than that, it's a really good gun. Not surprisingly, you'll see most people using it.