Orgyn - Tanky Lawnmower
 Ogryn Build - Warhammer 40k: Darktide 

Regular hordes: spam heavies to proc bleed which procs up to 60% damage resistance from Delight in Destruction while also regenerating up to 28% toughness per swing from Best Defence, Smash Em and Confident Strike. The club has insane stagger so all the little guys will be on the ground bleeding after one hit, giving you the damage reduction and taking them out of the fight so you can knock down the next wave and repeat the process. You're basically invincible in a horde.

For massive hordes or for groups of elites, use combat ability to charge into the crowd and press back (S) to cancel the charge as soon as you hit the last enemy. You want to be as close as possible to the enemies when you end the charge so you can then spam lights with up to 50% damage from Trample and 25% attack speed from Indomitable. This is the Lawnmower Mode. Makes mince meat out of anything smaller than an ogryn. 

For Ragers, the heavy swing stagger them hard, so they can't attack you. 

For Mutants, Snipers and solo specialists/elites, throw a rock. Rumbler is also great for these (except Mutants, always use the rock against them since it one-shots them for quick removal). 

For ogryns and monstrosities use the Rumbler. Crushers are the only real weakness since the Rumbler doesn't kill them efficiently, but you can heavy swing at their head to stagger them and you can bull rush them to knock down a while group of them.