I agree with fritzer Deadlifts really bring my traps out, also I think your best mixing it up, doing dumbbell shrugs, barbell, something I found effective was calf-raise machine shrugs, and don't forget standing upright rows too they get your traps
Last week I did a seat of heavy Dumbbell shrugs supersetted with lighter I felt my traps the day after, with a great burn in them !:
10 x 50kg drop 10 x 30kg
10 x 50kg drop 10 x 30kg
10 x 50kg drop 10 x 30kg
10 x 40kg drop 10 x 30kg
I really enjoyed that, felt it for a day or two after too !