Well, Quare, it appears that no one really read your post.

I find that the Cactuars are constantly a nuisance. They aren't particularly hard, but they hurt. Also the Tonberry started out as a not so hard enemy but they've evolved to be quite a challenge.

My favorite reoccurring enemy is the Coeurl. Its that catlike thing with LONG whiskers. It is known to do Blaster, which reduces your HP to 1. A pain in the butt. It was known as something different in VIII, but it was there. (It becan with an L)