Depends on the format, really. Pre-Reflections, I had a pretty effective Stupid Swarm deck. Basically, you use only 1-cost minions, have a fellowship that can cycle real well, then build up 8 minions in your hand and play them all at once.
Orcs have a ton of 1-cost minions, so this strategy uses a ton of them, plus
Isengard Warrior to help you stop
Greenleaf.
This tactic isn't foolproof, as any sort of Ring-bearer support, especially
Bounder, can help him survive the swarm. But it can be a nice surprise and catch your opponent off-guard. Plus, even if they do survive the swarm, there's always the odd chance you can use
Isengard Tinker to discard a half dozen Orcs to get a bunch of wounds on his fellowship. I retired the deck after Reflections, as it became too difficult to overwhelm some of the ARBs.