Monster of the Week is fucking dope.
I prep the game for less than an hour a week, and I'm able to run 5-6 hour sessions on it.
The game always moves forward. Investigations flow smoothly without stall-outs or navel-gazing. There's generally just one combat.
A story emerges naturally, without me having to plan some course of events. I'm just as surprised as the players about the way things turn out.
It's definitely different than pretty much all other games I've run, but I'm really enjoying it.
Meanwhile, in the other side of my brain, I've been yearning to do a Stars Without Number game, as I haven't had the chance to run it since before I went to grad school. (Except for the one-shot I did at KantCon this past summer) Alternately, a B/X game with weird science fiction shit going on in the background. Sadly, I can't seem to get any local traction on this.