Add match...with pattern matching (like F#)
F# has an amazingly powerful pattern matching feature built in (match..with).
Like a turbo-charged switch..case statement.
This would be so powerful in C#. But PLEASE make sure you implement the feature that allows the match case to be pushed in to a variable for use in the pattern itself.
match x with
| 1 | 2 | 3 -> printfn "Found 1, 2, or 3!"
| a -> printfn "%d" a