I've only ever received one of six types of poison: Centipede, Spider, or Giant Bee (Weak or Mild of each.) I've never gotten anything stronger, and I've never even seen the non-combat poisons. My concern is not so much that I always get the weakest or second weakest types, but rather that the types I get are incredibly limited. I would really appreciate seeing a better variety, especially the sorts of things you could conceivably put in a bottle, or food, or else poisons that affect mental stats or have atypical reactions.
http://nwn.wikia.com/wiki/Category:Poisons
A list of the default poisons, if someone does update this. (assuming it's broken, not sure myself)