Welp, while I check whether my other list, buried deep already by other topics, still has some good ideas, gonna start a new one. How are these?
1. A sewer pipe, on which above the exit is written an arrow pointing to the pipe saying "To Wonderland"; entering it causes you to fall into another dimension, almost completely composed of garbage and waste.
2. A soccer ball that, if kicked into a goal, causes everyone who sees it to celebrate like mad continuously until they die of cardiac arrest(or, in rare cases, begin celebrating so much they end up dismembering themselves)
2b. What Kingreaper suggested.
3. A cloud that sucks up water and grows bigger by doing so; when not absorbing a body of water, it will autonomously move to the nearest body of water.
4. A picture of a child that, if you touch it, will cause the child to grab your hand and pull you into the picture, causing you to also appear in the picture along with the child.
5. Two side-by-side statues; if you see them, they will start attempting to communicate with you via email, chat, cellphone, telephone, anything that allows you to communicate wirelessly; they do this under one persona. If you don't reply, or if your reply doesn't satisfy them, they will…well, haven't thought of it yet.
5b. The above; the statues contain the souls of two people; they try to call for help by doing the above. If you don't answer, they'll spam all your possible communicative devices and programs with a cry for help, asking to be freed.