Along with heating the outside, I've used cans of compressed air, upside-down, to apply a nice frost to the wedged in part. Usually in a Heat >> Penetrating Oil >> Freeze cycle. Between the oil and the mechanical act of heating and cooling I've gotten some pretty stuck parts free.
The other thing I've done is carefully work on the sacrificial part with a Dremel bit or a small drill bit. Sometimes you can relieve enough stress to allow the stuck part to flex.
The worst one was getting a halfshaft off of a parts car to return as a core so I could take my Eagle down to get the halfshaft. It was much easier though, since both the nut and the shaft were sacrificial and I could ruin the thread with the drill. Two runs with a wire bit down between the nut and bolt and it came off easy! I definitely didn't have a nut cracker that big.