I'll add here some plays that I make with Roslyn.
1 - Rewriter that take query comprehension syntax and rewrite it to corresponding fluent syntax.
This is a sub class of a bigger class that do the rewrite, among other things. Hence, it may be that part of the code will seem redundant. I kept the query as is, without removing any redundant parts.
2 - Rewriter that take an instance method and convert it to a static method