1 - Write a 4-letter word on the board. E.g "LOVE"
2 - Tell students it's the first word of a list.
3 - Tell them they will think of new 4-letter words to continue the list;
4 - They can only replace 1 letter to form a new word; they can't add or delete any letter.
Example: LOVE - LIVE - DIVE - DICE ...
Students play together as a class. You can establish a minimum number of words for a prize; 15 words for instance, so that it's challenging for them.
It's a great opportunity to test your students' range of words and foster a lot of speaking.