Pittsburgh Steelers linebacker James Harrison hasn't been fined for an illegal hit in quite a while, be he can be sure he'll get one in the mail from the NFL this week. On a play in which Cleveland Browns quarterback Colt McCoy was rolling out of the pocket, McCoy dumped a pass off to only get absolutely crushed by Harrison.
As you can see, Harrison led the shot with his head hitting McCoy right in the helmet. I don't know if I'd call the hit dirty, but given his history with hits and fines, Harrison should know by now to wrap up and hit with his shoulder rather than his helmet.
On another note, Colt McCoy came back into the game a few plays after the hit. Immediately after the hit, McCoy laid on the ground for quite a while and looked clearly dazed on the sideline. It's curious with the crackdown on concussions that McCoy would be allowed to re-enter the game. A few plays after McCoy returned, he threw a bad interception in the endzone.