Just for a bit of variety, I recently picked up and painted a handful of secondhand Tau. I don't play 40K any more these days, but I have a liking for the look of the Tau. It was a pretty quick and dirty paintjob, I wanted to practice getting a unit painted and game ready in minimum time. Still, I think they've turned out pretty well.
I also have a few drones and a handful of pathfinders that I might paint up. I may even then dig out some of my old Imperial Guard models and have a few games set on Curwen, using either the old Rogue Trader rules (I've recently picked up a second hand copy) or Necromunda (say what you like about GW, making the specialist games free was a GOOD thing).