Here is an easy-to-use rubric that is based off of the 6 Traits of Writing (Ideas, Organization, Voice, Sentence Fluency, Conventions, and Presentation). I include a brief description under each heading giving clarification to what each category means and have also added on a section for Supporting Detail.
The rubric is based on mastery with no points listed, just titles like "Novice" "Getting Better" and "Wow!" This way, you can use it as a formative or assign the point values of your choice.
The last feature is the back side (if you print it double-sided). If offers a place for not just teacher comments, but student comments! This is great for your students to write a response after they get their rubric feedback, or for them to fill out before turning it in so you can see what they think of their writing.
For more ideas on adding creativity in your classroom, check out my blog: www.creativeteachersclassroom.com