My father was head honcho of the CT SWAT teams for awhile in the mid-1990s... anyhoo, he got to try out some nifty stuff, and bring his teenage sons along for the ride
My personal favorite was the MP5 that cast a hologram down onto the gun; the hologram was a picture of the target, and there was a laser sight on the hologram, but not on the target in real life. This way, the target has no way of knowing they are about to be toasted.