Keep the mic plugged in so you can give voice commands to your team without taking your finger of the trigger of your weapon. Repeat what keller tells you into the mic and the team will do it as if you had switched the button.
When you play the Fremont Street level look for a ledge on one of the buildings that has a bottle of Axe cologne. When you shoot the bottle the neon roof of the Fremont Street Experience will change to an animation of a girl in a bikini promoting Axe items. This sequence is then followed by a sequence with outtakes and early animations.