Some people are good at developing games, but sometimes they have no inspiration. This topic is to explore, brainstorm ideas. You can say what game you would like to see, what setting, what crazy game mechanics you thought about, etc. Go wild, think of your post as lego blocks that could be used in a bigger structure. Also, since it's brainstorm, the idea is that your idea could lead to another, so it doesn't matter if it's "very very original", no judging, just pure creativity. Finally, let's talk only about audio games.
I'll start with some whacky game mechanics!
1) A game that would involve typing on the keyboard, you would do better the faster you can type. For instance, you could fight ennemies with words. There could be a giant word graph that this word is strong against those words but weak against those and it would be real time combat, hence you have to type fast. Example: water is strong against fire, etc.
1-b) Another similar idea would be a puzzle game where you would have to guess words to solve puzzles. The words would materialize with sound effects.
2) On mobile, use the accelerometer. We don't need to see the screen, so during combats, we could hold our cellphone like a sword and fight having audio clues with our headphones, swinging our cellphone like a wii mote.
3) Use the microphone. We could have a game where we need to record sounds that are similar to in-game generated sounds. It could be a multiplayer online game where you record a sound like a car passing by and then another player would have to replicate that sound. We could then use cross correlation between the target and matching sound to calculate a score and give points. To avoid issues with the recording sound part, it could be a game generated sound and two players would have to match it and the closest one wins. This could also be something to say when casting a spell or whatever, the power of the spell depends on how closely it matched. All of this is to avoid repetition during combat games.
4) A game where you use a Midi device as a game controller. Requires a musical instrument or midi controller. Basically, you could play a game by playing piano, the game would react to chords, scales, arpejios, etc.
Now game settings / ideas:
5) A game where you are super rich and everyone tries to steal your money. You have to try to keep the most money while making more.
6) A game where you are a doctor and try to save lives.
7) A game where you are god and can control natural catastrophies like earthquakes, tornados, volcanos, thunder, etc. Don't know the goal of that game.
8) A game where you must spread a disease on the entire world kinda like pandemic. Talking about the setting, not necessarily the gameplay.
Have fun! Think outside the box.