I miss Sinfest, shame it ended so soon.
On the subject of comics that are still running, I actually like a theory I heard that a lot of the game changing mutants died from more mundane causes then some far reaching conspiracy. Things like locals and even family who freaked out at the scale of their power and killed them or tried to exploit them to similar results. It doesn't quite hold up to what we know in universe but it would be an interesting idea on its own.