Still, sticking with something light for this, as I wanted to give the question the credit it's due.
From ME, by ME, I ask you, The Question.
If you had a giant laser capable of inscribing things on the moon, what would you carve?
And please, folks, keep in mind we are ONLY discussing the moon-carving applications here. Pretty much all the other uses (yes, even the beam-splitter ones) can be taken for granted... Although I have to admit, the one you're thinking about is pretty cool. :3