Khorne
1 Herald
8 units of either Bloodletters, Bloodcrushers or Fleshhounds
All units gain +1 attack while within 6" of one another.
All units benefit from the Heralds loci if they are within 12" of him.
Another formation:
3 Skull Cannons, squadron, may fire as one with an Apocolyptic Blast with AP3 and still Ignores cover, ouch.
Tzeentch
Herald
9 units of either Pink Horrors, Flamers or Exalted Flamers.
+1 Strength to all Warpflame attacks.
All units within 12" of the Herald benefit from his Loci.
Another formation:
1 Herald
9 units of either Screamers of Tzeentch or Burning Chariots
Chariots can do Slash attacks, inflicting D6 str 5 ap 4 hits on a unit they move over. Screamers get +1 hit.
All units within 12" of the Herald gain his Loci.
Nurgle
1 Herald
7 units of either Plaguebearers or Nurglings.
Enemies may not fire overwatch at units from this formation.
All units gain the Heralds Loci while within 12".
Another formation:
1 Herald
7 units of either Plague Drones or Beasts
All units gain Hammer of Wrath with poison 4+
1 unit within 12" of the herald may take a leadership test if they pass they can reroll failed charges and gain +3 attacks. If failed they must attempt to charge the nearest enemy.
Slaanesh
1 Herald
6 units of either Fiends of Slaanesh or Daemonettes.
Any enemy units in combat suffer -1 WS and -1I
All units within 12" of the herald benefit from its loci.
Another formation:
1 Herald
6 units from either Seekers, Hellflayer, Seeker Calvacade.
All units move 6" when running or moving flat out.