Invective rules - Hi RoF and ammo regen but if you want to use Thorn as your Exotic get a Felwinter's rifle (it aint no shotgun) I have a secret handshake ( not from vendor, full auto I use also)

Secret handshake from Vanguard vendor gives you more bang for your buck. Hammer forged plus shot package means you will kill at a farther distance and it shoots pretty fast for a shotgun.

I've been running Two To The Morgue for as long as I can remember. It's such a beast, especially against minotaurs and praetorians. In PVP it is decent, although the range seems to lack against Secret Handshake and Invective. I looked at the Vanguard's Secret Handshake which has Arc damage (a good compliment to Two To The Morgue's void), decent range and impact, and has Hammer Forged AND Shot Package perks. I thought this was the shotgun I need, so I started saving up for 2 weeks to get enough marks and a commendation to buy it. Sure enough on the nightfall, right before I was about to get a commendation, a Judgement VI was rewarded to me. Not only get I get insanely lucky with luck in the chamber, hammer forged, and shot package, but its base range and impact is better than Two To The Morgue and Secret Handshake. I cannot wait to fully level up Judgement and ruin everything.

I use the vendor Judge all the time in pvp. It's actually really good. The only problem you have to worry about is Felwinters Lie catching your before you can catch them

Secret handshake from vanguard is your best bet. Comes with shot package. It's a pvp beast