Most of the weapons in Black Ops 2 are unlocked by playing online and reaching a certain experience level or by completing missions in the single player campaign; attachments will be unlocked in the same way. If there’s no mention of a weapon in the Classes game menu that means that the weapon is already unlocked and available.
Assault Rifles
Can hold 300-450 rounds. High power and effective at medium range. Available in single player only.
Fully automatic assault rifle holding 30 rounds. The first two round are fired faster. Available from Level 55
Automatic assault rifle. Available in single player
Semi automatic assault rifle holding 25 rounds with light recoil and medium damage. Available from level 22
Semi automatic assault rifle holding 60-80 rounds. Available in single player e Zombie mode
Fully automatic assault rifle holding 105-140 rounds. Available in single player
Single fire rifle with high power effective at medium range holding 160 rounds. Available in Zombie mode
Fully automatic assault rifle holding 660 rounds. Available in single player
Full automatic assault rifle with high mobility and light recoil holding 30 rounds. Available from level 31
Fully automatic assault rifle with low recoil holding 630 rounds best used at medium range. Available in single player
Assault rifle shooting 4 round burst in rapid succession holding 32 rounds. Available from level 49
All rounded fully automatic assault rifle. Available from level 4
Fully automatic assault rifle with nice range and damage holding 30 rounds. Available from level 40
Semi automatic assault rifle with the best damage for assault rifles holding 20 rounds. Available from level 46
Assault rifle firing 3 round high damage bursts holding 30 rounds. Available from level 4
Fully automatic assault rifle holding 30 rounds, high fire rate with moderate recoil. Available from level 4
Assault rifle with the best mobility and accuracy, firing low damaging 3 round bursts best suited to long range shooting. Holds 30-45 rounds. Available on single player
Handguns
3 round burst pistol with a high rate of fire and moderate recoil holding 15-135 rounds. Available after completing the Suffer With Me misson
Double action high damage revolver pistol firing 28 gauge shotgun shells. Available after completing 5 challanges during the Celerium mission
Versatile semi automatic pistol with a large magazine holding 20-180 rounds. Available after completing Pyrrhic Victory.
Fully automatic pistol incorporating recoil mitigation technology holding 15-135 rounds. Available after completing the Fallen Angel mission
Semi automatic pistol best used at close range, holding 7-63 rounds. Available in single player
Semi automatic pistol best used at close range holding 8-72. Same stats as the M1911. Available after completing the Celerium mission
Semi automatic pistol with high damage at close range holding 10-90 rounds. Available after completing the Time and Fate mission