I'm torn myself, though I'm not a W40K player, I enjoy both Dawn of War games, and some of the books. The Tau are good, but so are the Imperial Guard...
Also, the Guant's Ghost's series make then very likeable.
...For this very reasonEchelon_3 said:Imperial Guard.
Considering every monster / horror / superhero movie shows the military being powerless (usually resulting in a few unlikely heroes saving the day), it's nice to see the horrors of the galaxy crushed under the bootheels of ordinary men and women.