If it is in a blind hole I would attempt to pull it out before I resorted to drilling it.
To pull it out, first weld a small pile on top of just the pin, TIG welding is best, but with a properly sized washer around it to protect the casting a MIG welder may work.
Once you have enough sticking up to grab a hold of weld whatever you need to to it to be able to use your slide hammer.
You don't have anything to lose by trying, as you can grind the weld off flat and drill if you have to.
If you do get it out consider drilling all the way through to avoid the problem next time.
Grigg
