One person says a letter. Then each person, one at a time, has to say a letter, forming a word. The letter you say has to have the possibility of forming a word, but if you end a word you get a point. The first person with 5 points is out. If you think that the letter someone says doesn't have the possibility of forming a word, you can challenge them, and they have to tell you what word it could form. If they don't have one right away, they get a point.
Example: One person says A. The next person says N (even though AN is a word, 3 letter words or less don't count). The next person says I, then M, then, A (ANIMA can lead to a word but isn't a whole word itself). The person that says L ends the word ANIMAL and gets a point. A new round starts.