I was just in a bookstore and I saw a book that had pictures that reminded me of Marathon. On the back one of the spaceships looked the pfhor's ship. On the front the characters helmets looked like they were out of Marathon. I thought his machine gun was kind of like the one in M2. The book was published in 1987.
It was a book from the Stainless Steel Rat Series by Harry Harrison. I forget which one. I didn't see it on amazon.com.
http://www.amazon.com/exec/obidos/ASIN/0441004229/qid=990913924/sr=1-47/ref=sc_b_47/104-8171216-2335945
