Popular as in guns people talk about a lot.
Mine are:
Hopscotch Pilgrim - I have one with outlaw, braced frame and hidden hand but I just don't like the feel of it and went back to Messenger.
Suros Regime - pre-1.2 nerf, I had one but hardly used it in PvP
The Last Word - I bought this from Xur the second time he sold it and it was my go-to PvP handcannon, now, I don't even touch it.
Thorn - nope, used it right after they 'fixed' it and never really liked it
Hawkmoon - I love the gun but I've been having trouble getting consistent with it in PvP (great in PvE)...I'm making progress.
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Thorn. Hate the sights.