Roguelike ideas that I'll never get around to making:
ParanoiaRL: Unlike most roguelikes, this one takes place on a single large map with corridors. You could, in theory, walk right up to the exit and win. Unfortunately, you're a Red, and the exit is Ultra Violet, and Locked with an Ultra Violet Key. Map making would start by drawing the UV layout, layering the Violet, Blue, etc. on top. 95% of the time, when corridors crossed, it would take the lower value (but not always). If the random guys walking around find you with gear outside of your grade, or in a corridor or room out of your grade, they attack. You (probably) die.
Serving the computer will get you rank. The computer asks you to do exceptionally random stuff.
Elemental Plane of Dungeon: Your small town has been sucked through a rift. It's farms and fields are gone. People are starving. The only answer is to descend into the cavern system to find food and supplies.
Seriously. Kinda like Ravenloft, only it's 'Dungeon' instead of 'Fear'. Interesting features: 1: The metagame is that you aren't really playing the adventurer so much as the town. Each 'adventurer' starts from scratch with low stats, but the health of the town, the training and EQ that's available to you, etc, is dependant on what previous adventurers have brought back. 2: The Dungeon : The ground under your feet is constantly shifting. Coming back from a run, things may be different. Alternately, you may wander back into a level that a previous character has been through (not that more monsters haven't moved back in and looted the corpse). 3: Stasis. It may be possible to secure the first few levels, giving space for the town to grow food and open new shops and houses. It may also be that certain subterrainian levels are stable enough to place outposts on. 4: Food. You aren't likely to starve yourself, but the townspeople might.