I'd love to see a Haskell Tool similar to the already existing Python and R-Tool.
Haskell is a great way to handle data without side-effects. I know I am probably pretty much alone with this suggestion, but I wanted to share it anyway.
I also know Python can do basically everything Haskell can do, but it isn't as beautiful and effective as it is in Haskell. Haskell brings many logic operators and great syntactic "sugar" out of the box. Things like pattern matching with input parameters is just amazing in Haskell and would require way more code in Python.