Buzzwords by Dan Harlan

You show your audience that all you have is a list of words and some cards with letters written on them. The words are different, and even contain a wide variety of letters from all parts of the alphabet. Your spectators choose a number, and you count down the list to the word in that position. Then you reveal that the cards you are holding spell the exact word they chose. The best part is that the list and the letters never leave the screen. No way you could have switched them, nowhere for you to hide.