Favorite critter would be low lvl stuff like Goblins, pigmies, kobolds and such because there are so many and at low level they can be a real challenge.
I love dragons but they are too exploitable. Monk speed always helped Shivla catch people who tried to run.
We did a tail slap ability in ns3 that was so sweet if only it had an animation.
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I like humanoids becuase of the huge variety we can do with armor/skin color. Orcs and stuff that only have a few models were never as much fun.
Amazons were sweet becuase I got to use the half orc model and go nuts with variation. Same with Bandits, Half Dragons, Drow etc.
NWN2 allows for scalable models which just makes so many more possibilities.