Ask HN: TodoMVC or anything else

I want to build a complex demo (but not too complex) in a framework of my choice (in my case Ramaze/MongoDB/sequel) But I think TodoMVC might be too simple to full utilize the frameworks.

What other kind of examples could one make?

My initial thoughts are a project management demo (with acl), or a Holiday Request app.

Are there any other ideas for apps I could build?