For a gender reveal, you could go with the standard blue or pink cake. Or one of my friends that's really into baseball, someone packed blue powder into a ball and pitched it at him. He hit it and blue powder went flying everywhere. More recently, I've seen someone squealing their tires and they somehow made the smoke pink. None of those methods were good enough for Taylor Calmus. He built his own Rube Goldberg machine.
If you're not familiar, think the board game Mouse Trap.
It took him three days to set it up with the help of some friends and it spanned over his entire house. Check it out.