. Innovative user interfaces that use natural language processing, image recognition, gestural control, new hardware devices, and the like.
. Generative games, where the gameplay or world is dynamically generated based on choices the player makes.
. Gameplay based on the emotions of (and interactions between) non-player-characters, where the player influences the characters to achieve some goal.
. Interactive storytelling, where the plot or dialog of the game changes in a fine-grained manner (in contrast with more typical discrete "branching points").
. Subtle emergent gameplay, where game systems interact to provide evolving situations. Physics-based gameplay would be an example of this. Another example would be a game with complex interpersonal interactions, like alliances and feuds between groups.
. Novel sorts of multiplayer interactions -- online, at the same machine, with wireless devices, using image recognition, or whatever.
from CFP of Experimental Gameplay