Warriors of Chaos: Nurgle Daemon Prince with Death/Slaanesh Level 4 with Cacaphonic Choir, Chariots, Chimeras, Skullcrushers, Marauder Horsemen, 1+/3++ re-rolling 1s Exalted BSB on a Daemonic Mount, Throgg with Trolls.
Daemons of Chaos: Papa Nurgle, Plaguebearer Horde, 2x Skullcannons, Plague Drones, as many Beasts of Nurgle that can be fit into the list.
Dark Elves: Level 4 on Death, multiple Pegasus Masters, Witch Elf Horde with Cauldon, Dark Riders, Executioner horde with Bloodwrack Shrine, 5-15 Warlocks, multiple RBTs.
High Elves: Loremaster with Book of Hoeth, White Lion Horde with Banner of the World Dragon, Frost Phoenix, other inconsequential stuff.
Orcs and Goblins: Savage Orc horde with Shrunken Head, Trolls, multiple war machines (surprisingly good at countering Warriors of Chaos, and therefore quite popular).
Empire: Light Council, Halberdier horde, tons of Demigryphs, Steam Tank.
Vampire Counts: Multiple Terrorgheists.
Lizardmen: Slann with Death/Wandering Deliberations/Focus of Mystery, or Tetto. 2-5 Saurus characters (mix of Scar-Vets and Oldbloods), Skink cloud, Temple Guard horde (36+).
The above seems to be the most common lists that I see. Ogres and Skaven used to be right up there, but can they even be considered power builds anymore given the above? I'm not so sure.