Shotguns can be packed with buckshot, slugs and rubber baton rounds. On certain maps it may be raining and this will make your mission hard by reducing visibility. On snow maps you will also be able to dress your guys in really cool, white snow uniforms. You can also throw a Frag Grenade or Flashbang with either the right or left arm in this position. There are also crouching movements.
Different weapons have different zoom sizes.
No longer will you be able to sniper in with any weapon. The zoom is now modeled much more realistically. An MP5 will zoom about as much as a pistol in Rainbow Six. When you finished your mission you can run a cinematic replay. This will help you see what went wrong.