Stick a carbide bit in the ignition face using gentle pressure and a high speed drill.
After you get through the case hardened face on the ignition and get a reasonable sized hole cut you can go to a regular drill bit and wallow out the soft stuff behind it. If you go deep enough you can use a screwdriver to turn the ignition and drive the car if you want. I drove mine until I figured out MB would sell me a replacement cylinder.
