There's a marine unit/model included in Warcraft III (if you finish Reign of Chaos on Hard you'll see a short in-game cinematic featuring Marines, Zerglings, Hydralisks and Space Orks(??)).
You can find the unit under the Object Editor's Unit Editor. Go to Neutral Passive > Campaign > Units > Marine.
I did slightly edit the skin used by the model for To the Bitter End, but the model itself is the same.