More ammunition:
To gain more ammunition kill an enemy when he is reloading his weapon and you will get a full magazine for your weapon.

Ubisoft logo:
When you first start the FBI level, immediately after the woman shoots out your cuffs, go to the center of the room with the three computers. You will find the Ubisoft logo acting as a screensaver.

More ammo:
Wait until an enemy reloads his weapon before killing him. Now shoot him before he fires his gun and you will get his full magazine for your weapon.