Straight forward list of some common motor faults:

1. Shaft - Imbalance, Misalignment, Wear
2. Rotor - Imbalance, Rotor Bar Faults, Loose Rotor, Eccentricity
3. Stator - Stator Looseness, Incorrect Air Gap, Winding Fault
4. Motor Bearing Housing -Mechanical Looseness, Misalignment
5. Rolling Element Bearings - Cage, Ball/Roller, Outer and Inner Race Defects Looseness within the bearing
6. Motor Feet - Structural Looseness/Soft Foot
7. Base-plate/Foundations - Structural Looseness, Twisted Supports
8. Motor insulation - Insulation breakdown

 If I've missed any other common faults, please take a bit of time to add them in as a comment below.