Correct_Carlo
Arcane
Also, you can do everything an adept and engineer can do just by using squad powers. That's why I always pick a class based on which class has the most interesting guns + unique powers. It's why I always end up playing either Vanguard or Infiltrator in the end, as they both have the most unique playstyles in ME2 and ME3 (in ME1, class doesn't matter as much because all of your powers are the same as your teammates).