Hmm, i have a few serious ones, and then there's the ones that jokester's use on amazon. "Air in a spray can" or "Instant - undies, just add water!" There's a lot you could do;
Looking at amazon and youtube for inspiring ideas for your project is a good way to start gathering ideas for what you might want to make. Now, im not saying to steal other ideas, but maybe gather a little and make your own idea with help of things on amazon or things with silly items.
Hope this helps!