It depends on how you are playing them. Are we talking Speed Freekz, the Greentide, or some other, more insane form of random Orkiness? As far as units go, Deffkoptas and their ability to outflank can provide some pain where it is needed. Bikes are great for that permanent 4+, and Lootas that get 3 shots each can decimate infantry or shred transports, so long as they hit first. Burnas are great against other hordes like Tyranids, other Orks, and stuff like that. Almost any list can stand to have a mobile fire base like a Battlewagon, and it makes a great linebreaker if you include a Deffrolla. It all depends on how you choose to play your Orks and what you are trying to accomplish. Hope that helps.