I thought about some silly (one-star, possibly) weapons to introduce as an April Fools gag.
* A Flourish with a giant green olive impaled on it.
* A Troika shaped like a giant fish.
* Guns that shoot "BANG!" flags or bubbles.
* A bomb that looks like a big whoopie cushion.
"Foolish" costume gear could have really garish colours or a "Kick Me!" sign taped to the back. This forum is probably more creative than I am, so have at it: what would be funny or silly like this?
For a true Apirl Fools feel, mess it more. A 5* weapon with 1* damage, mixed up stats on description, etc.
But the most important part, how would you introduce these items?