Insanely foolish and over the top Imperial Guard deathstar:
Lord Commissar -- power fist, carapace armor, dedicated chimera
Techpriest Enginseer -- 5 servitors
Priest -- eviscerator
Priest -- eviscerator
Priest -- eviscerator
Priest -- eviscerator
Priest -- eviscerator
______
Total = 570 points
The commissar and priests are independent characters, so they join the techpriest's unit. All 12 of them hitch a ride in the commissar's dedicated transport. Priests grant re-rolls to hit in combat; half of the unit has an invulnerable save; lots of high strength power weapon attacks. You could give some of the servitors heavy weapons for some firepower, but you'd probably never be stationary to shoot them unless you bunkered up in the Chimera (which might be advisable in Annihilation missions...). Heavy weapons also replace the servo arm, which would be unfortunate because you want this unit wiffing in combat!
Obvious downside: Lots of kill points on one-wound models
I think I earned a for this. (Watch superhappyrobot lean back and put his hands behind his head like Han Solo after he says, "Sometimes I amaze even myself.")