Technically you never see a marine with a USP .45 
Glad someone caught that.

You're wrong about the roostering back thing though, you have to rooster back the slide on a pistol if it's single action. I'm also almost certaint that it's up to the the specific police department when it comes to what guns they want to use. I've seen SWAT teams with P90s in some states and then M4s in another, glocks here, M9s there. There isn't really a standard.
Not if the gun has a slide lock/release switch, which almost all handguns do.
Also you're pretty much right about the police thing. There is no standard, and stations/individuals can use their own selection of firearms, but it's pretty loose-ended. The general United States Police handgun is considered the M9, because
even though the officer or the station can choose different firearms, the most common/most widely used handgun is the M9.
Throw the knife.
There's your stealthy weapon.
Ignore OP
Do no thinking
???
Make stupid post