Weapons fall into 4 categories, which correspond to the body types - Heavy, Medium, Light, and Pistols. All characters are able to carry two weapons, one matching their body type, and one lesser weapon. So Light players are limited to having a SMG or light rifle main weapon, and a pistol. If you want a true automatic rifle or a shotgun you need to move up to medium body type, and Heavy is required for the biggest and most powerful weapons. You aren't forced to choose from any single group though, a heavy player could have a pistol as a secondary weapon if they wished, or even carry an SMG as their main if so inclined.
In addition, to answer his question about snipers. There are no real snipers, only rifles with a scope. They ressemble snipers, but they're not intented for the casual sniper gameplay (Camping + hardscoping) There will also be no quickscoping, which is a good thing.
SD want to keep the action limited to close quarters, face to face. They don't want you picking off people from across the map.