Topic: grammar and vocabulary / warmer.
Time: 5 to 15 minutes.
Divide the students into teams, separating them into two or three rows, facing the board. First student from each row comes to the board. Call out a letter. Students must write down all the words they can think of that begin with that letter. Call "time's up" after about 20 seconds. Second students come up. Give them a different letter. The row with the most correct (and correctly spelled) words wins.
This game is especially suitable to be a fun, lively warmer.