Creative Drawing
Before kids reach their teens, their drawings tend to spill out whatever is sitting in their heads. A child that age often has no idea how much a picture gives away, though now and then they'll narrate the whole thing to you, telling you what they're drawing and maybe the reason behind it. That makes drawing a useful tool when you're working with children in therapy, and it works both ways: the child draws, the therapist draws, and somewhere in that back-and-forth an issue can start to loosen.
None of this is fancy. You don't need any artistic skill, and neither does the child. The supplies are cheap and you've probably got most of them lying around the house already if there are kids living there. Old computer printouts work fine once you flip them over to the blank side. Crayons or colored pencils cover the basics, and a wide range of colors helps more than a few. For an older child, markers or paints open things up further.
What the therapist reads isn't only the subject. The colors a child reaches for, the action happening in the scene, where the figures sit on the page, who got included and who got left out: all of it carries information. Sometimes you'll ask a child to draw something frightening or painful, say a visit to the emergency room. If they hang back and don't want to, the therapist can pick up the pencil first and have the child direct the drawing, telling the adult what goes where.