One shots

Until I get another regular game going to replace Delta Green, it seems that one shot efforts are going to be the order of the day. I already mentioned the Godlike "demo" a while back; these are some of the other candidates.

• Call of Cthulhu: Tatterdemallion (from Fatal Experiments). I've ran this once and had a great time. Investigator casualties were high but not total, and I recall it actually ended fairly well - for the world at large, if not the surviving heroes. In a one shot this is, of course, not so important... if no one gets out alive, the players cannot pester me into continuing the story! I can only hope my Carcosan Pallid Dice arrive from Chaosium before we play.
• D&D: Underdark. I was asked to run a mini campaign (okay, technically not one shot; so sue me) featuring the archetypal underground races such duergar and drow as PCs. I did not promise anything (and if the person in question happens to read this, I'm still not promising anything), but it could be interesting. However, I don't have an Idea for such a game yet.
• That Western Game. My "Serenity Project" is not intended to be a one shot either, but it could begin with one to familiarize people with the rules and give them a chance to fine-tune their characters before kicking off the actual story. Perhaps a prequel set during the Civil War?

What to do, what to do...