Key broke inside the ignition - 1986 GMC S-15

This will depend on how much of the key is left. You could try this:

WARNING: This could cause a worse problem

This assumes that you have the part of the key that is not stuck in the ignition. If the car is not already in "park", turn it to the park position.

Get a tube of superglue and apply a very small amount along the part of the key where it broke off. Try not to get any on the sides of the key. You only want it on the "break line". (If you get too much on, let it dry and then peel it off with a knife or other tool and start over. Don't try to wipe off exess with a cloth or paper, it will just make a mess.)

Immediately after applying the glue, hold the steering wheel hard to the right or left, and then push the key in as far as it will go and hold it as still as you can for about two minutes. Next, start rocking the steering wheel gently back and forth. If the key is stuck in the "Park" position, the steering wheel will only move a little bit.

After you determine how far back and forth you can move the steering wheel, try to hold it the middle and then gently try to extract the key. If the key will not come out easily with gentle pressure, try rocking the steering wheel while you gently pull on the key.

Good Luck