The only common Hexatonic (6-note) scales we find in modern western music are the blues scale and the "whole tone scale." Both of these scales are rather new to western music, starting in the late 19th and 20th century. Of course any 7-note scale with one note missing can be regarded as a 6 note scale though in most cases the sound is not distinctly different from the original 7-note scale.
The half-step intervals for these two scales are:
To play a whole tone scale on a keyboard, play the notes with the red dot (3 black, then 3 white, etc):
Of course you can translate all the notes up or down by any number of half steps. For example, if you move up (or down) 1/2 step, you play two black keys and then four white.