You'll get a million different answers to this one including the old "whatever works best for you" fall back. What I will say is that I believe this game has the most balanced selection of weapons in CoD history. For me at least that translates to them all being good, in the right hands and right situation.
Having said that, my top three re: kills are:
Even 6 down the list I have 3,333 kills with the FAL for a decent spread of use. The gun I have the most fun using is the KSG as I believe it takes more "finesse" to post decent numbers and it is much more connection dependent than some others.
Pistols are also fun and the best they've been IMHO.
Most OP class is
FAL with Stock + Red dot
Ghost and flakjacket
This depends on if you are very accurate and have a fast trigger finger and you need a solid connection.
Other powerful classes are MSMC with quickdraw, the Skorpian dominates at close quarters for game types like hardpoint and KC and when keeping distance M8A1 is very accurate and powerful but again you need to be confident with your accuracy
There is no best gun overall. Everyone has different play styles. Theres best guns to suit peoples play styles and reactions. I personally love the m8 due to me having fast reactions and being a caucious player. But I wouldn't say its the best gun in the game, I would say its the best gun in the game for me!
Depends on your playstyle, doesn't it? Personally, I go for guns with a high rate of fire, because I'm relatively slow and not a good shot. But for a sniper (although all of the maps I've played are terrible for sniping) I go for high damage (and silencer), because I don't have time for more than one shot usually.
I gotta go with the an 94
When playing solo
Rds, stock and silencer
With flak jacket, toughness and dexterity
With a tac-45
When playing with people take out the silencer for fmj
Burst firing those long shots is so easy
Prefer it to any smg besides on overflow where I pull out the mp7 with long barrel, QuickDraw and fast mags
I can't use the msmc iron sights for medium distance shots. The mp7 is so much easier for me
The best gun to use for league is definitely the m8
Playing in pubs 6v6 its way to hard to jump shot and drop shot with that just gets me killed.
But playing league 4v4 its so much easier to dominate with that gun
And man I must say fmj is so under rated
Everybody head glitches and having fmj just destroys them so easy
Way better to use on an ar that sacrifice using an lmg and moving slow
Can't go wrong with an ar in this game considering it can dominate at mid range compared to smg and even close range, the average pub players aim is so bad you can take them out using an ar that has minimal recoil
Just my 2 cents