Ok, I wanna see your list of stupid game ideas.. this is just some I could think of at the moment - I'm sure there's plenty more. [:)]
Daikatana - depending on an AI buddy..
A few years ago, having a smart AI buddy along your side to help you complete your missions was a huge selling point in singple player FPS games. Daikatana promoted it as one of its key game elements. (Anyone remember that Bruce Willis game on the PSX? The MAIN selling point of that game was that Bruce Willis was your friendly side kick who would help you battle it out through the whole game, and yell out whacky action one-liners while he's doing it. Unfortunately, the development team couldn't get the whole AI buddy idea to work decently at all, so in the end, you just played as Bruce Willis on your own. [:)])
Unfortunately in Daikatana, if your buddy dies while you're playing, it's game over for you too. There are funny stories of people just leaving those 2 Daikatana sidekicks at the beginning of the mission, wiping out ALL the enemies in the level, then going back to bring them through.. [:)]
Metal Gear Solid 2 - directional microphone
This was a non vital part of MGS2 where you aimed a directional microphone at people *in the hope* of listening to their conversations... if you didn't aim properly (and hey, it was darn hard to see the actual people you were aiming at since they were behind walls!), then you missed what the characters were on about.. the conversations, however, weren't vital to solving anything, so in the end, the whole directional microphone was just a gimmick to deprive you of some story. Neato [:)]