
Honest Hearts would've been the perfect place to introduce new passive creatures, but hopefully Lonesome Road will do!
I give you...
http://en.wikipedia.org/wiki/Pronghorn Monster deer with horns made of win and awesome.
http://en.wikipedia.org/wiki/American_Bison They've been hunted nearly to extinction, it's time to take back what's theirs!
http://en.wikipedia.org/wiki/Desert_tortoise (heck, I'd take a retextured Mirelurk!)
So, what mutant or normal animals do YOU want to see in future DLC?