I have just uploaded a couple of videos onto youtube going through some German grammar. At the moment I have done accusative and dative pronouns and adjective endings following indefinite articles.
Make your youtube videos a quiz or create an interactive create your own adventure story. Start the story, students create the endings as videos and users can choose which ending they want, or have students first create the middles and then choose a middle different from their own to then create an ending. What are your ideas?
One of my Yr 10 students made this grammar tutorial on Relative Pronouns without much guidance from me. This isn't a topic that I normally teach at Year 10 level so I'm very impressed!