A while back I had a yellow tang that gotten so aggressive I had to get him out. After trying other methods with varying results, I got up around 2 am and shined a light directly at the tang. He was stunned/disoriented long enough for me to scoop him up easily in a net, avoiding the coral and rocks. Once in the net he was P***ED! The deed was done though, without any noticeable long term effects and he went to a new home.
By far the easiest method I ever tried. He was obviously traumatized for a short time, like any method, but no cost or damage to rocks or coral.