Not a list of ideas but an approach on the solving this question

  I don't belive that one can find a guaranteed successful story on any topic. It is not just the plot that matters. It is much more the language, the approach taken on telling the story. There are many things invowen into a good story. Just finding an idea shouldn't be that difficult. First of all, we have to admit that creation of something new is not trivial nevertheless there are many non-unique successful stories.
  Thus, we can start from the object of your story - the knight. Then I would suggest to write that word in the center of a whiteboard and then start writing nouns that are related or not that related to the object. Write them anywhere just like - steel, dirt, knife, sword, shoes, friend, dog, horse, space, start and so on. In anoter part of the board write adjectives that could describe the knight and the nouns. Then write verbs that could describe the interaction between the previously written "words". At this point you'll have a mess of words and you'll have to start bringing them to an order. Try to link notions and actions together and to the center object with links. When you are done with it I'm sure you'll have plenty of simple and some advanced ideas on the future plot.
  Then it is a matter of the approach that you'll take on telling your story. You'll have to pick a timeline, decide wether for example it is going to be a mix of past and present or entirely present story and so on. At the end you'll have an idea on language and style.