Well, Nadia's thread title was pretty open-ended, so I'm going to post my competitor for most beautiful yucca. This is Yucca linearifolia 'Dusky Blue'. It was next to another yucca, but I didn't even check to see what that one was. No flowers, so @Nadia White Rock wouldn't consider this competition at all. I don't suggest touching the leaf tips as I did to see if they're sharp.