Mauler is the Title of a more powerful type of fully automatic Combat Rifle. At the same level it is likely to be stronger than a Machine Gun or Havoc as it always has a displayed increase to damage on the item card. Maulers are also typically inaccurate weapons, however their rates of fire do not suffer nor do their magazines. Becaue of that Maulers are exceptionally good weapons to bring into tight quarters where cover is abundant for the enemy, like in Old Haven.
Examples are on the talk page.