Shooting Infinity is a non-canonical power-up that appears in the map Riesige Anlage and is exclusive to the Nazi Zombies game mode.
What it does:
Shooting Infinity acts much like a death machine power-up, but can be very useful or not very useful depending on your gun. Shooting Infinity puts a "pause" on your gun that shows that the ammo out of or in your gun is not depleting (so there is no need to reload). So, you have infinite ammo for both your guns. Now, if you have a beginning pistol, this power-up will be close to useless on later rounds, but if you have something like a Wunder Waffe DG 2, then this is the best thing ever!
Why is it useful:
Well, it is extremely useful for those who have Double Tap Root Beer. Also, running out of ammo can be at times very critical.
What it looks like:
Simple, it looks like the Infinity sign (a sideways 8 if you don't know). This replaces the death machine so it radiates a light blue light.