illustrator

The more powerful but also an expensive method, the official logos were made in a similar way to this.
(This method is more complex than the blockbench method)

BlockBench

Not as powerful as the Illustrator method, however it is free and really quick and easy to use
(I highly recommend using this method rather than mine-imator)

Photoshop

Not as powerful as the Illustrator method, however it is still a powerful method