[giffc]

I admit to finding the name a bit off-putting. There is an amazing low-fidelity, highly iterative, and agile-friendly sketching tool and it is called a real pencil. On gasp paper.

Not that I don't use digital tools too, but I am often surprised how rarely people go analog when it can be invaluable.

[archivator]

True but often you need to present your design in a more professional environment and throwing together a sample UI in a matter of minutes can come quite handy.