Create 2 categories. For example: things with 4 legs and things with 2 legs.
Then add a random word that doesn't fit either category, which is the detective.
Each student gets a piece of paper with a word written on it, but they cannot look at their word.
It might look like this:
lion, table, penguin, kangaroo, chair, ostrich, hippopotamus, gibbon, ant
4 students are in the 4 legs category and 4 students are in the 2 legs category.
The detective (ant) is alone.
The 1st student begins by looking at the card of the 2nd student and making a 1 sentence description of the word.
The 1st student is not allowed to tell anyone what the word is.
The 2nd student can guess what their word is and the 1st student will tell them if they are right or wrong.
Moving clockwise, the 2nd student will do the same for the 3rd students and so on.
Whoever can guess the 2 categories and the detective is the winner.