Bigger traps
 

What is the best workout or exercises that one can do to make his traps bigger?

Shrugs.

Power Cleans
Power Shrugs
Farmers Walk

Shrugs, but dont do the circular motion shrugs. trap are the back of your neck and down. so squeeze your shoulders up and behind your neck. also do holds with them, if not all the time, some of the time. Holds can be anywhere from 1-3count holds

deads are also great for them

Deadlifts

Really heavy partial Deads have served me well (280+), as have heavy Power Shrugs.

Deadlifts, power cleans and shrugs are 3 great options.