Kunal Bhatia
Kunal Bhatia reviewedAtomic.io 2.0Ultra fast, scalable and fully collaborative prototyping
 RecommendedPros: 

Most powerful tool to prototype ideas without using code and they push the envelope with newer features before others think of them.

Cons: 

If you're looking to do something completely custom and you can't hack a solution together in Atomic, I'd turn to Framer.

Atomic is my go-to solution for ideating, creating something to test with customers, and communicating with developers. You can get an idea of how I use prototyping tools in general here. It includes an overview of many tools in this space.