Today I tried to get a snapped off bolt out of my daughter's impreza's torque converter.
I didn't want to heat it so just tried the reverse drill trick and an extractor tool - No joy. (those extractors don't really work for me -- they often snap off on me, sucking even more).
Getting frustrated, I hammered a torx bit into the drilled hole and it turned right out! Torx are slightly tapered, are very hard and happen to grab the edges of the hole really well. Maybe this is old trick - if it is, I'd never heard of it so thought I'd share it.
(If it is indeed an old trick, this must be what if feels like for a monkey to discover tools :)
Remco