Here's a fun game I've used in my ESL classes to introduce my students to adjective clauses (e.g. who, that, which, etc.).
First, students write two sentences, one about someone in the room, and a second about something in the room. Tell students to keep the person/thing a secret. You can a model a few examples (e.g. This is a person WHO likes to teach English / This is something THAT is used to write on the whiteboard)), and then have students guess the correct answers.
The worksheet I pass out to students is below. Feel free to use or adapt!
Directions: Write 2 sentences describing someone and something in the room using adjective clauses. Remember, for people use ‘who’ or ‘that;’ for things, use ‘that’ or ‘which.’ After you are finished, read your sentences and your group guesses who or what it is. Keep your information secret so that they guess.
(Someone) This is a person _________________________________________________
(Something) This is something ______________________________________________