costs 15 rage without the rage reduction talent, and replaces sunder armor as of 2.3m once you hit 50 and you're prot spec. Post 2.3, it applies sunder armor, while causing a decent amount of dmg (which can crit), and it refreshes the application each time it's used. and just like sunder armor, it has no CD, so you can use it infinately, so long as you have the rage to cast it. only draw back is if you get diarmed, but that's what they made taunt and shield bash for.

hmm. its like slam, but slam is accutally more usefull.