If the anime was never completed, Then you're in luck. You can continue the story by reading the completed manga. This list has basically the same rules as a couple of my other ones, includes anime originally based on a manga, no...
This list is for those non-sequel shows that were marked as watched by 3000 people or less. I also excluded shows that aired recently and was watched by more than 2000 people since they will reach the "3000 watched" limit soon.
I'm always looking for good anime and I happened to stumble upon these 60 series that are basically unknown. I felt the need to share with others. I recommend each of them. Some more than others, but they're all worth the try...