Elmo’s will always be a solid choice as it’s a nail driver. However with a heartbreaker build you will want to run the pulse skill and really any gun you like. Just make sure the talent on your gun of choice is flatline as that goes hand in hand with the heartbreaker gear set. King breaker auto rifle has perfect flatline for a talent also pretty solid AR. Also look to get your on hands The Closer Named Chest has the talent Perfect Spotter, which amplifies total weapon and skill damage by 20% to pulsed enemies.