Jeremy Gilbert made an awesome clicky toy. The goal of the project was to create a toy that is fun to use, be tactile, light up, and make fun and satisfying noises.
After looking at different options to get the right “clicky-ness”, a 5V relay was used. Jeremy discovered that you get get louder clicks if you overdrive the voltage. While this probably isn’t so good for the relay, he felt that since the actual duty cycle is so short it was worth the risk.
The clicky box of awesomeness is field programmable so that when new suggestions come up during user acceptance testing (performed by his 3-year old daughter) they can be implemented right away.
The write up on Jeremy’s Hackaday project offers a good narrative of how he approached the challenge of getting the right clicky sound and feel.