Hammering in a 12pt torx that's a little bigger than the hole has always worked for me. Just be sure to buy a new plug while it's out.

 

The easiest way to remove a stipped bolt head is the get a bolt extractor. There is no drilling, heating, filing or hammering needed. All you would have to do is put the correct size on the bolt and turn counter clockwise. It gets tighter and tighter until it grips and loosens. Something like this.

http://www.sears.com/shc/s/p_10153_1...bolt+extractor

 

i dunno why this is really an on going thread. you shouldn't have put the drain bolt on that tight to begin with which mean it shoudl be hard to get off at all. try to stick the air gun down while tightening drain bolts!

 

sears, home depot and lowes carry special sockets for removing stripped bolt heads