Wikipedia has this on their HK416 page. Does it sound fairly accurate?
"HK416/417 Users:
-Indonesia - Indonesian Marine Corps Counter Terrorist Unit, Detasemen Jala Mengkara (Denjaka).
-Netherlands - The Netherlands Army special forces unit Korps Commandotroepen selected the HK416 over other tested assault rifles to replace their Diemaco C8 assault rifles. The weapon is shown on several photos from the unit's recruitment day. The HK416 is currently (2008) the standard assault rifle of the unit.
-Norway - On April 11, 2007, the Norwegian Ministry of Defence signed a contract for an initial shipment of 8,200 rifles to serve as its new standard assault rifle, replacing the AG-3 that has been in use since 1967. It is slightly modified, with a different stock and pistol grip. The deal also included the purchase of 6500 HK MP7. Delivery is expected in the first half of 2008.
-Turkey - Turkish Army has tested 9,000 units of the HK416 manufactured domestically as the Mehmetçik 1 by MKE, and decided to adopt it as a replacement for the currently issued G3 rifle. The Mehmetçik-1 will differ from the original HK416 in some details, like the use of a different metal alloy in its construction. This will probably to allow MKE to manufacture the rifle by the cheaper and simpler procedure of Metal Injection Molding rather than forging.
-United Kingdom - The HK416 is used by the British Special Air Service
-United States - It is used by the U.S. Army's 1st Special Forces Operational Detachment-Delta, various other Special Operations Command units including DEVGRU, US Capitol Police SWAT, and the US Army's Asymmetric Warfare Group. "
I've also heard that FBI HRT also has them in service.
"HK416/417 Users:
-Indonesia - Indonesian Marine Corps Counter Terrorist Unit, Detasemen Jala Mengkara (Denjaka).
-Netherlands - The Netherlands Army special forces unit Korps Commandotroepen selected the HK416 over other tested assault rifles to replace their Diemaco C8 assault rifles. The weapon is shown on several photos from the unit's recruitment day. The HK416 is currently (2008) the standard assault rifle of the unit.
-Norway - On April 11, 2007, the Norwegian Ministry of Defence signed a contract for an initial shipment of 8,200 rifles to serve as its new standard assault rifle, replacing the AG-3 that has been in use since 1967. It is slightly modified, with a different stock and pistol grip. The deal also included the purchase of 6500 HK MP7. Delivery is expected in the first half of 2008.
-Turkey - Turkish Army has tested 9,000 units of the HK416 manufactured domestically as the Mehmetçik 1 by MKE, and decided to adopt it as a replacement for the currently issued G3 rifle. The Mehmetçik-1 will differ from the original HK416 in some details, like the use of a different metal alloy in its construction. This will probably to allow MKE to manufacture the rifle by the cheaper and simpler procedure of Metal Injection Molding rather than forging.
-United Kingdom - The HK416 is used by the British Special Air Service
-United States - It is used by the U.S. Army's 1st Special Forces Operational Detachment-Delta, various other Special Operations Command units including DEVGRU, US Capitol Police SWAT, and the US Army's Asymmetric Warfare Group. "
I've also heard that FBI HRT also has them in service.