I mangled a couple bolt heads trying to use the wrong tool to loosen them. Which leads me to tip number one: Don't do that.
But when you have done that, E-Torx sockets can work really well to grab something that is rounded off a bit but maybe not destroyed all the way. I had a handful of 8mm bolt heads that I couldn't turn with a regular 6-point socket and that also wouldn't engage with a 12-point. They needed a deepwell socket so my normal bolt extractor sets wouldn't work. I turned to an E12 deepwell socket that I bought to work on der Scheßwagen. Perfect fit on the bolt and they came out with no drama at all.
