Good exercises to develop your trap or trapezius muscles. 

Dumbbell Shrugs

Holding dumbbells at side, stand in good body alignment (abs tight, chest up, back straight). Keep arms straight and elbows fixed. Slightly bend knees, keeping feet flat on the floor. In a controlled motion, maintaining body alignment, draw shoulders up as far as possible. Contract traps fully, without compromising form. While maintaining the controlled motion, return dumbbells to starting position. Do not allow muscles to relax before next repetition.