This technique can be used as a starter or recap activity and takes little or no preparation.
Invite students to come up with key words from your subject. Type / write them randomly all over the whiteboard. Around 12-15 is a good number.
Next invite two students to stand on either side of the board. Now ask a student from the rest of the class to ask a question, or give a definition the answer to which is one of the words on the board.
The two students at the board then compete to Splat the correct word with their hand / a fly swat / a rolled up newspaper.
For example, if a student says "A reason why some houses fall into the sea", the student who splats "Coastal Erosion" wins that round.
The other student sits down and is replaced by the student who asked the question. This encourages students to participate as questioners, because they may enjoy going up to the board.