Ok so I was writing this earlier and Steam didn't like me going over their 4096 character limit so I hit the back button to edit and found out that everything had been cleared. So here's a more TL:DR version:

Weapon data for each game in the Call of Duty series has always been available from the game files. This guy here has already exctracted it and tabled it up quite nicely.

As you may quickly notice weapon damage has been reduced overall. Guns which do 40 or 35 damage will kill in three shots but do note that at 40 dmg you can kill with two headshots. Guns now also have much more noticable recoil. The Kiparis, G11, HS-10, Stoner 63, PSG-1 and CZ-75 are "Classified" weapons in their respective categories which become available for purchase after obtaining all other guns in its category.


Submachine Guns:
Most SMGs kill in 3 shots at close range (about 19m) and 5 at long with the exception of the Skorpion which kills in two at "close range" (a measly 5m). My picks for "best SMG" are the AK74u for all-round use and MPL for rapid assaults. The AK74u does have quite a lot of visual recoil though so some may prefer the MP5, while Uzi with Grip is a good alternative to the MPL.


Assault Rifles:
Most kill in 3 at close range (about 38m) and 4 at long except for the semi-auto M14 and FAL which can 2-shot at close. I put the M14 ahead of the FAL as it has a more even recoil while I pick the G11 over the M16 in terms of burst weapons (remember that the G11 is unlocked by buying all assault rifles though).


Shotguns:
Shotgun range maxes at 15m but don't expect to kill much past 10m. Olympia has a high dmg output but is restricted by mag size, SoH is recommended. The Stake out is pump action and carries four rounds but gains an accuracy boost when ADS. SPAS-12 is probably the all-round shotgun in this game although it's nowhere near as deadly as its MW2 counterpart. The HS-10 is similar to the SPAS bar mag size, but it can apparently be Dual Wielded.


Machine Guns:
All of them are 3-shot kills can have a smaller ammo count except the M60 which carrier 100 rounds and can 2-shot within 25m. Each MG seems to fill a different role so take your pick.


Snipers:
Not much change here. You have your bolt-action L96A1 which 1-shots from the abdomen up (including shoulders and biceps) and your semi-autos which look almost identical to each other.


Handguns:
3-shots at close range and 5 at long except for the Python which is 2 and 3. The Python reloads so slowly though that I would not recommend it without the Speed Reloader attachment and/or SoH. CZ-75 definitely seems like the best handgun with its superior mag size as well as *drum roll* full auto. While you do need an attachment to go full auto I'm sure I'm not the only one who's more then a bit concerned about it getting into the hands of the masses.


Well there we are. Have fun and start enjoying the game once it's teething problems are solved.