Was just about to say that. I've only played a few games of zombies... ever, but I got the War Machine out of the box and was elated. That joy melted away as I tried to waste a group of zombies only to launch a super bouncey ball at them.
It's pitiful. Un-upgraded, it does 100 damage (without multipliers) to the zeds (enough to 1HK on round 1, 2 on round 2, etc if multipliers were taken out of the equation) Upgraded, it does 200 damage without multipliers and gains a LOWER RoF to boot.
So yeah. (even with multipliers it is the worst gun in zombies history)
I still stand by my claim that the starting pistol is the worst. Even on level one it requires three headshots to drop a zombie. And when you're in the later rounds and you die and respawn, you can't even kill one zombie with it, let alone the 16 others flanking it.