I have seen quite a few especially endings to Anine Here are a few that bugged me
Sailor Moon (The ending and the few characters that where missing)
Gunsmith Cats They pretty much did 3 episodes and thats it. I mean they had a whole heap of stuff to choose from.
Ranma 1/2 (read the final book and you will see a fantastic battle that would have been awsome to see. To bad the Anime was done first.)
The last one I was so dissapointed with was a series call Seven Of Seven. The manga was more mature and had alot more depth but then they made the Anime so kid friendley it took away all of it's charm.