Josh Barnett.
I always found him to be one fo the most technically sound fighters and he rarely fails to impress me when he gets someone on the ground.
He seems know exactly what he's doing and I would pick him as one of the most complete and entertaining fighters.
Of course, there are others but I thought I would leave a mention about Barnett
I just he loses that fat arouind his waist and he would look somewhat like a real fighter