It can only be found and used in Zombies. The only place you will find it is in the mystery box through random selections of guns.
You will not find a method to guarantee getting the Thundergun The related link has more information on the thundergun
Not in the form used in Black Ops, no.
Knife. no...
The Thundergun is a Wonder Weapon featured in Zombies and can also be found via an Easter egg in the campaign mission "Numbers". Quoted from the related link for Thundergun
you get it from the chest, it is a gun which can blast up to 24 zombies
The thundergun is not available in multiplayer mode but canbe obtained in zombies mode by means of the notorious mystery box.
no
Upgraded thundergun with an upgraded Ray gun and monkey bombs
NO you have to get them from the mystery box. Sorry.
you cant you can only get it in world at war on the second level but you can get the thundergun on the the level "numbers"
no but you can get a thundergun. Its in the Kowloon campaign mission collect 2 tape in recorders
By random chance from the mystery box. In spite of rumors nothing will increase your odds and there are no cheats