DS loves the toothpaste in middle.of Oreos trick. He knows it's coming but it still cracks him up. Plus we make a cheesecake with the real center.
Last year DH and DS pranked me with a caramel covered onion.
We pranked DH with a squeezed out paint tube trick (hot glue to make it look like the paint spilled) all over his computer. It was obviously fake on second glance, but we have a good picture of his face when he first saw it.