Sin Episodes demo / Arena mode
Now, Sin Episodes emergence is an absolute bargain at $15 and one of the reasons for not releasing a demo with Emergence was that its cheap price meant that it wasn't too much of a risk to shell out for.
Now, I'm sure Ritual are at work with new features for Arena mode as well as multiplayer and Ep2. I mean, if you could introduce more features into Arena mode like introducing more enemies like the mutants and chaingunners, then it'd serve as an excellent demo for Episode 2.
One Arena mode map, a good selection of weapons and enemies and the ability to post non-anonymous play stats onto ladders and then I'm sure it'll be a success.