Just curious... what is he wearing?

I suppose someone from Wikipedia has already combed through it.
GnySgt. Hartmann's ribbon rack*:
Bronze Star, Purple Heart, Combat Action Badge, Marine Corps Good Conduct Medal, Marine Corps Expeditionary Medal, National Defense Service Medal, U.N. Medal,
Vietnam Service Medal, Korean Unit Citation, Korean Service Medal, Republic Of Vietnam Campaign Medal
He also is wearing the Expert badge for Rifle and Sharpshooter badge for Pistol.
*the only one I couldn't identify was the one in the very bottom left of his medals rack.
SSgt (ret) R. Lee Ermey's actual ribbon rack*:

Meritorious Unit Commendation
Marine Corps Good Conduct Medal with two bronze Service Stars
National Defense Service Medal
Armed Forces Expeditionary Medal
Vietnam Service Medal with one bronze service star
Republic of Vietnam Gallantry Cross with Palm
Republic of Vietnam Campaign Medal
Rifle Expert Badge
Pistol Sharpshooter Badge
*After retirement, R. Lee Ermey was also retroactively awarded the Drill Instructor Ribbon due to his prior service as a Marine Corps Basic Training Instructor as well as the Vietnam Presidential Unit Citation for unit activities during the Vietnam War.