I'm also in for a multiplayer game, though I won't be able to commit much time. I'd also avoid a shooter game, with the same reasons as Germanunkol gave above.

A "click and go" type of game is fairly easy to programm, hack and slay action like diablo, or it could be more puzzle-oriented. It just happens that i'm currently programming a "click to walk" prototype which is developed into the MMORPG direction, but I could simply remove the login/account management code and we'd have some code to look at or even start from. I'm currently using the Anet plugin which we should not use as it's not free and we'd get into licencing issues. lets rather show what the native system can do. I've done it before in C-Script, maybe I can dust off that old code again and get it into lite-C. As said before, we could create the the basic level geometry from prefabs if its indoor, and then add details through models or decals. That's pretty much what my plan is for my current project, though
you can check out my blog (see signature), but there isn't much info yet.

on the other hand: singleplayer can be a lot of fun, but telling a story can be really difficult, as we just can't compete with the AAA story titles. the game shouldn't take itself too serious.