"Non-cheating" AI

[Resinence]

I've been working on a project for a while and have been putting this off, but now would like to implement AI that doesn't cheat and can pathfind effectively, but I've never really done anything to do with pathfinding in a 3d world (heightmap terrain + Mesh's) or AI that has "vision".

So I was wondering if anyone here had any links to an open API or Class Library, or maybe just somewhere to read up on this? (Starglider? ) Although I prefer C# it doesn't have to be .Net, I'm comfortable with C++.

But while I was thinking about this it brought up a question that I may as well post here so the thread doesn't get ignored and fall down into oblivion. If true AGI was created, how ethical would it be to have a crippled AGI as the enemies in a videogame? Would you equate it to slavery?

Edit: And performance isn't an issue, what I want is something really quite heavy with high "intelligence" which I can downsize if needed.