I recently corresponded with a Lieutenant in the Marine Corps who mentioned in a neutral, or possibly ironic way, that he had seen General Mattis give a talk at Quantico. Here's what the often inaccurate Wikipedia has to say:

On February 1, 2005, Lieutenant General Mattis, speaking to a forum in San Diego, apparently said "You go into Afghanistan, you got guys who slap women around for five years because they didn't wear a veil. You know, guys like that ain't got no manhood left anyway. So it's a hell of a lot of fun to shoot them." "Actually, it's a lot of fun to fight. You know, it's a hell of a hoot. It's fun to shoot some people. I'll be right upfront with you, I like brawling." Mattis' remarks sparked controversy, and General Michael W. Hagee, Commandant of the Marine Corps, issued a statement suggesting that Mattis should have chosen his words more carefully, but would not be disciplined.

General Mattis popularized the slogan "no better friend, no worse enemy" among his command. This phrase became central in the investigation into the conduct of Lieutenant Ilario Pantano, a platoon commander serving under General Mattis. Lieutenant Pantano shot a pair of prisoners on April 15, 2004. He said that he thought they represented a threat. Lieutenant Pantano emptied two entire magazines into their bodies, because he wanted "to leave a message". He then scrawled General Mattis's slogan over the bodies.

EDIT: He is portrayed by Robert John Burke in the HBO miniseries Generation Kill.