Then there's the Daewoo K2 and derivatives. This is the rifle used by the South Korean Army. Many features, such as the bolt carrier group, are derived from the M16 and the gun uses the M16 magazines. However, it has a gas piston system derived from the AKs. It is somewhat similar in appearance to the AR18.
I bought the civilian version (AR-100) one back before they were banned in 1994. I haven't put a lot of rounds through it but I've never had any issues with it. The folding stock is pretty cool. http://en.wikipedia.org/wiki/Daewoo_..._Industries_K2