The P90 is a Sub-machine gun found once in Black, in Naszran Foundry.

A Standard FN P-90 PDWS


The P90 is likely to have the highest rate of fire in the game, and at 100 rounds, the second largest magazine size. Combined with the high accuracy single-shot fire mode, this gun is very useful in a brawl. It's only downside is that in fully automatic fire, it is incredibly inaccurate, so, burst fire is recommended. It also has a slow reload, so it is recommended that you switch to your second weapon if you have to reload in a fight, or hide. Another incredibly useful (and unique) thing is that is both accepts assault rifle AND sub-machine gun magazines, meaning that you never run out of ammo.