Not exactly a gag gift .. but a bit of a prank. My middle son used to say that he could always tell what his Christmas gifts were.
This particular year, I'd gotten a substantial raise, and was able to buy the children gifts substantially more expensive than other ones, and I had also purchased a ring for myself. So I wrapped up a note in the box my ring had come in, and put it under the tree for Mr. "I know what's in the box". The note gave him directions as to where to go to find his actual gift (an iPod). Leading up to Christmas day, he looked at that wrapped gift under the tree, and was completely baffled. I told him that it was a nose ring.
The next year, I got him a particular Lego set--and that was my crowning achievement. I hid the wrapped gift *in his bedroom* in a place that I was fairly certain he would not look. Under the tree was a wrapped box that contained one of the really small lego sets (like it wasn't even in a box, just a plastic bag with less than 50 pieces to make some sort of droid) that was from the same Star Wars category as the thing he really wanted. That box also contained a note directing him to the place where the prior year present had been hidden. That present was another lego set (Luke's sand speeder) with another note "This is not the present you are looking for ... your actual present is [directions as to where to find it]"
This particular year, I'd gotten a substantial raise, and was able to buy the children gifts substantially more expensive than other ones, and I had also purchased a ring for myself. So I wrapped up a note in the box my ring had come in, and put it under the tree for Mr. "I know what's in the box". The note gave him directions as to where to go to find his actual gift (an iPod). Leading up to Christmas day, he looked at that wrapped gift under the tree, and was completely baffled. I told him that it was a nose ring.
The next year, I got him a particular Lego set--and that was my crowning achievement. I hid the wrapped gift *in his bedroom* in a place that I was fairly certain he would not look. Under the tree was a wrapped box that contained one of the really small lego sets (like it wasn't even in a box, just a plastic bag with less than 50 pieces to make some sort of droid) that was from the same Star Wars category as the thing he really wanted. That box also contained a note directing him to the place where the prior year present had been hidden. That present was another lego set (Luke's sand speeder) with another note "This is not the present you are looking for ... your actual present is [directions as to where to find it]"