I currently have 2 projects that I'm working on. They are both in the prototyping phase, but show relative promise.
The first, a party game designed for 4 players, local splits-creen style. Each player is given their own, randomly selected maze to navigate. The first player to complete their set of increasingly difficult mazes is the winner. However, players can mess with each other, Mario Kart style, with items and weapons they find in their maze.
The other game is, on the surface, a standard RTS game; ordering units around, upgrading structures and researching tech, trying to outwit the opponent. But sometimes, it's not enough for the player to command the whole army. Sometimes, the player wants to get right into the action themselves, FPS style. I often hear, "If you want something done right... you have to do it yourself!" So why not make a whole game out of it?