To me I like quite a few of them, I quite like the KVolt and X43 Mike, they're cool, but not so great (it seems Kvolt had a damage increase since patch 1.4? It's not bad now...)
Although my best weapons are the Scarab (grenade attachment = fun!


For sidearms I recently unlocked Extended Mags for AY69, it used to be meh, but with 40 rounds it's really awesome

As for worst, it's definitely the Hammer. Fires slightly faster than Majestic, does slightly more damage than Nova, and overall svcks.