Every developer has ideas that are discarded on the basis that they are unfeasible, under-developed or rubbish. Here are some of my ideas for the Xbox Live Indie Games channel, now yours, for free!:
1) "Things I'd do for 80 MS points"
With the addition of video support in the Xna 3.0 framework, it is now trivial to include clips in your game, or in this case, showboating application. Think of it as Jackass-Lite - film a series of short videos, each beginning with someone saying "For 80 MS Points, I'd ..." before they do something silly, embarrassing or mildly painful. Have two videos available in the trial version and a further ten or so unlock when the 'game' is purchased. The whole thing would be entirely transparent and shameless, and would be a financial cash-cow. Probably.
2) Remake "Star Warrior"
A sinclair spectrum game I remember fondly, that was ostensibly a Galaxians rip-off with an unusual twist. The gameplay was split into three sections, the first being the standard Space Invaders fare and the second a slightly unusual section where you had to avoid multi-coloured asteroids while descending onto a planet. The third part was the most interesting, a tense standoff between our hero (a magenta figure eight pixels big who would furiously dance on the spot) and the Psychotic Cyborg (a small white ball with a menacing black pixel, which I took to be an eye). The hero would have to enter a yellow maze to get to a blue diamond, protected by the cyborg who would semi-randomly twitch and jerk its way around the maze. As a six year old, I remember that making a dash for the diamond was a truly exhilarating affair, as the Cyborg would make a terrifying 8-bit screechy sound as it moved, and would mercilessly hunt and shoot your frantic, dancing hero on sight.
Modern gaming, replete with autosaves and checkpoints, can be quite lacking in tension and atmosphere. Remake the above, along with some intricate form of permadeath, and you have a genuinely stressful game with an intensely rewarding payoff.
3) "The Race Card"
Pick a card game, any card game. Play as normal until one player pulls out the Race Card. Upon playing the Race Card, their opponent must turn off their console, feeling slightly ashamed and confused.
4) Indie Band
Approach one of the many unsigned bands flouting their wares on Myspace and the ilk. Create a short application that displays photos, images, band-motifs and lyrics along to their music. Release their album or EP for 400 points and split the profits. It's limited in that the music is non-transferable and only playable on the Xbox itself, but you may get some media coverage for the unorthodox route to market (the band being interested in publicity, you in sales). I'd much rather this flood the market than massage apps.
5) Be the bad guys
Some games have attempted to let you play as the bad guy (e.g. Dungeon Keeper, KotOR) but usually in a way that doesn't have an especially meaningful impact on the gameplay. You still play the game as normal, be it shooter, RPG or Strategy, except you have evil ends to evil aims instead of good.
One departure from this would be to make a game where you truly get to be an typical Bond-Villain. It could be a bit like a tower defense game except not as dull, where you command dozens of inept, incompetent henchmen against an impossibly overpowered and good-looking AI controlled hero character (perhaps modeled on the Commando unit from the C&C games). Only through sheer attrition or blind luck are you able to take him down - perhaps he gets stuck on a bit of geometry and starts to swear. Or perhaps it's fairly easy to take him down, except the AI can restore the game from previous save points and you succeed by frustrating him to the point of exasperation, at which point he exits the game abruptly and you are returned to the dashboard, triumphant.
6) NXE 2
Make a game based on the Xbox (New Xbox Experience) dashboard itself. You essentially have a series of mini-games that are 'launched' as separate apps within the service, parodying existing games. The soundtrack could be "I made a game with 'I MAED A GAM3 W1TH Z0MB1ES!!!1' in it, innit?".
Point and Click Adventuring offers an opportunity to explore interesting and exciting areas with characters and storylines. Unfortunately the majority of titles, especially freeware games, instead prefer to explore safer and more traditional territory (You play Jacob Mackenzie, a Private Investigator with a murky past and a point to prove!). This may lend itself to traditional inventory-based puzzle-solving, but often doesn't do much in the way of providing actual entertainment.
As with film and music, I like to encounter things that I haven't experienced before. There are so many interesting topics to be covered, which first got me thinking about having a game where you play as a pregnant woman, where you navigate all the social pitfalls of dealing with a pregnancy that only you want. The player character would noticeable change over time, growing in size and a decreasing walk speed. How many times have you seen a woman giving birth on tv compared to in a game? How many games deal with the relationship and bond between a mother and her newborn child? Maybe the mechanics of such a game would turn out to be tedious, but I'd like to see it tried. It's not all about saving the world and blowing things up.
It should hopefully be easy to spot which of the above are rather tongue-in-cheek. Don't be fooled; very occasionally I do actually have some half-decent ideas. I'm just keeping those closer to my chest.
Edit: Star Warrior - that's the one. Added screenshot. Thanks, David.