Would you like me to [kill you] now?" asked Snape, his voice heavy with irony. "Or would you like a few moments to compose an epitaph?

Here lies Dobby, a free elf.

Snape raised his wand and pointed it directly at Dumbledore.
"Avada Kedavra!

I can teach you how to bewitch the mind and ensnare the senses. I can tell you how to bottle fame, brew glory, and even put a stopper in death.

Look...at...me..." he whispered. The green eyes found the black, but after a second, something in the depths of the dark pair seemed to vanish, leaving them fixed, blank, and empty. The hand holding Harry thudded to the floor, and Snape moved no more.

Yes, it is easy to see that nearly six years of magical education have not been wasted on you, Potter. Ghosts are transparent.