Trench Marine Doom is an improved (or rather edited) wad of Marine1.wad by Sergeant Daniel G. Snyder and World War Doom by MegaZombieman115. Both maps have been compiled into a single wad and is heavily modified and showcases what open battlefields would look like in Doom using only vanilla stock monsters (with a bit of Dehacked tinkering).
Intended to run with Eternity Engine (since I used some of Eternity's advanced bits 2 & 3) but ZDoom sourceports work too.
TMD.zip
MBF Dogs. And if I have the chance to use them, I usually have them side with the player. It's kinda fun to have them in your map. There's also the option to make a customized Dehacked of them so you have plenty of options to choose from.