This is a simple activity to practice "whose" that some of my JTEs have used. The only thing you need is a basket or two.
Start out by picking a student close by and ask them if you can borrow something on their desk, like a pencil case or textbook. Then ask the class "Whose pencil case is this?" They should answer "It's Yuka's pencil case" or "It's Yuka's." If they aren't familiar with "whose" and words that indicate possession, be sure to explain it to them before continuing!
Repeat this a few times with items on other students' desks. Whose pencil is this? Whose book is this? At some point, ask the student whose item you're holding and try to get them to say "It's mine."
Next, tell the students to choose one item they have with them and ask them to put them in the basket that you're carrying. It should be something they can remember if they see it (like a pen with a specific design or a well-used eraser) but not anything with their name written on it, since that would make the game too easy. If you're doing team-teaching, it helps to have two teachers collecting the items. Once all of the students have given an item, mix them up in the basket or baskets.
Ask the students to put their heads down on their desks, and redistribute one item to each student. Once every student has an item, they can put their heads back up. If any students have their own item, ask the class to put their heads down again and redistribute their item with a few other students to mix things up again.
Now that students have their own item, they need to ask their classmates "Whose ______ is this?" Their partner can answer "It's so-and-so's" or "I don't know." If it's their partner's item, their partner should answer "It's mine" and take their item back. Once the student has found the owner of the item, they can sit down.
If the students enjoy the activity, they can play another round with a different item. If the students don't want to part with their personal items, you could adjust the activity by having them use pictures that you hand out or they draw.