[adouglas]

Start with penetrating oil and patience. If the caliper is off the bike and drained dry, you might also use some heat but be careful. You don't want to melt sensitive pieces (e.g. piston seals) or start a fire.

If the hole is shot, you might try getting a Torx bit that's slightly larger than the hole. Pound it in good and solid with a hammer so you have a positive interference fit (you'll destroy the bit doing this, BTW). Then use a hand-held impact driver with socket on the bit to break the bolt/pin loose.

What this amounts to is that you're putting a hex-headed pin on the end of your stripped fastener, which gives you something to grab. Socket goes over the bit and into the impact driver, whack whack whack and if all goes well it comes loose.

I've done this successfully when I stripped out an overtightened bodywork fastener on my then-new GSX-R. The usual method (heat) was a no-go because it would have melted the body panel.

The trick is that you only really have one shot at this. If you strip out the hole with the Torx bit, you're going to be drilling the pin out. So be patient and use that impact driver, giving it solid, deliberate whacks (a dead-blow hammer is the tool of choice for this).