Monster Manual II has two monsters that fall under the OGL. The razor boar is one of them. A dire boar on steroids with incredibly sharp tusks. In D&D, their vorpal tusks decapitate, but are an extraordinary ability, not a supernatural one. Thus, I just decided to give them a huge armor divisor without granting anything more related to neck-cutting.
The infamous bane of all adventurers! This metal-smelling insectoid (on four legs, according to the picture) can rust metal with just a touch. Finally, I found an excuse to use the feelers from GURPS Powers: Enhanced Senses and smell-based Detect. I love sensory abilities.
The urophion is the result of implanting an illithid tadpole into a roper. The result is terrifying.
Now this is a very cool monster. Barely mobile, but able to camouflage against vision and infravision, it releases sticky strands to unwary prey and pulls it into its mouth.
That's just a giant giant eagle. Nothing special, just a big bird of prey, but is a staple of the fantasy genre.
The remorhaz is an arctic predator that shares its hunting grounds with frost worms, dining on frost giant, muskoxen, and caribou. It saves itself from cold not by developing an innate resistance to cold, but by radiating extreme heat that fries everything nearby. However, it can stop doing so to hide under snow and ice and surprise the prey.
This is another one of those monsters that nobody remembers. Probably because it's native to the Positive Energy Plane that is very hostile and has very few points of interest for the adventurers to explore.