In my opinion, the Shadow is. The Red Dot sight and suppressor coupled with the 1911's damage make it more useful than the 6P9 or whatever.
I still carry a .44 to kill tigers and such though.
The .50 cal sniper you unlock is not best from my perspective. It does a lot of damage, sure, but I prefer to utilize a suppressor. Makes things a whole lot cleaner.
As for the others, I wouldn't know. I usually carry my two pistols, a suppressed M700, and the Recurve Bow.