Ork's really are the best. Edit: also here's the colors for Ork's Red is faster, yellow is bigger explosion and makes it worth more, white makes it kill better (vague), purple is sneaky (you've never seen a purple Ork), black makes it tougher, blue is lucky, and green is the best cause Ork's come naturally green.
I hate to be that guy, but Jacob is wrong about some of this. Namely, Orks know about the warp and understand psykers and have some of the best short range teleportation tech in the universe. They do know how their weapons work; the waagh field just acts as a sort of magical wd40/duct tape mix that makes everything work more reliably than you'd expect.
