Originally Posted by dirtman

A little bit of heat works wonders too for the stubborn one's. (I don't mean take a torch to it, just warm it up, often a hair drier is all it takes).
I generally take a propane torch and warm the sprocket up just enough that its too warm to hold onto comfortably, then set the driver on the bar or old wrench and remove it with the chain whip. You don't want to turn it colors, just heat it up enough that there's a temperature difference between the driver and the sprocket. I've had a few that wouldn't even think of moving come right off by simply applying a bit of heat.
Heat only the sprocket, not the driver or the bar your going to use to hold it with. The sprocket will expand just a bit making it easier to remove.