(No DLC and this is as if you didn't do son of medici)
Best guns:
Urga Vdova (powerful, and wasting ammo isn't a problem)
Fire Leech (This gun seemed bad to me at first until i discovered how to lock on)
M488 (dont shoot to close, otherwise OP)
Peacebringer (at least more preferable to any of the pistols)
CS wrath
PDW-K (poblem? Ammo. Also a spelling error.)
Worst guns:
Pozhar (absolute worst gun)
UVK (great for destroying helicopters, and more stuff, but sucks at destroying stuff fast)
CS Negotiator (BAD gun, range sucks)
Urga vdova/automat
Little General/peacebringer (if you didn't do son of medici)
M488/Eden spark (DLC)
The automat is a good gun, as you just need to click once, and the reload is faster.
M488 is not good at close combat.
Little General is a good one since the damage increase.
Eden spark is DLC.