Now that I think about it, one of the more interesting entries I had into the US was from Kuala Lumpur to LAX. From the plane, there was a series of corners into ever narrowing corridors. Then, around the last corner, in single file, each passenger walked past a drug sniffing dog.
And then there was the flight into Frankfurt. Before the door opened, we were told to have passports out for inspection (unusual to have them out during disembarkation). Get to the door and there are two paramilitary police with automatic weapons, one with a dog, and another who was checking passports properly (hold it up beside your face to make sure the picture matches then read the information). I don't know what was going on, but they were looking for someone in particular.