So far one of my favorite is the Irwin bolt Extractor set. It lets you remove rounded off bolt heads. Saved me a couple times.
I found with these its best not to use impact gun it will cause the extractor's teeth to strip. Also when you place it on the bolt head use a hammer and tap it into place until
it firmly grabs and you aren't able to spin it by hand.
Irwin 394001 (Starter Set) http://www.amazon.com/Irwin-Industrial- ... +bolt+grip
Irwin 394002 (Expansion Set) http://www.amazon.com/Irwin-Industrial- ... +bolt+grip
![Image](http://i.imgur.com/fxCqWC7.jpg)
Here is a picture of 2 bolts I removed off my buddy's Evo X exhaust. The bolt were rusted in place and the head got rounded off. I made it worse trying to use vise grips.
![Image](http://i.imgur.com/VVKZFcA.jpg)
![Image](http://i.imgur.com/pmgjmTA.jpg)
![Image](http://i.imgur.com/pmgjmTA.jpg)