Best sling weapon?

What does everyone think the best weapon for Ballistic's sling is? So far I've been using mostly either shotguns or sniper rifles, I think the situational advantages of being able to quickly switch to a gold rated Longbow in a long range fire fight is great, especially if you don't have a long range weapon... Or the shotgun for close quarters combat. So my two favorites have been the peacekeeper and the longbow. 

I have also had some success using a devotion in it, and just letting loose a hail of bullets suddenly into a crowd of squads fighting.