Favorite beardie substrate?

We've all honestly used many different substrates for out beardies, lets admit that. But which have you grown most fond of, personally? the substrate you wouldn't mind using forever.
   
I've used almost everything and have switched back and forth between substrates. However the one I've used the longest and am most fond of is walnut shells. Not crushed like they used to sell, but ground, which is a little finer. My mature beardies (even one fat tail) have been on it successfully for about a year and instead of providing dangerous belly heat, I use this.