I really like this post. First of all, I have always had this strong attraction to Anti-Heroes. In most of the worlds presented where they are used, heroism would typically either result in a boot to the arse or a sword to the throat. Anti-Heroes don't seem to me so much a class of people different from heroes, but heroes who do what they have to to survive. Heroes are characterized as people who a) do the right thing, but b) go about it using only moral tactics. It is very rarely (in good fantasy, at least) that you find a hero that believes in "the ends justify the means." Now, granted, in awful fantasy there's always the melodramatic, histrionic hero who weeps after killing and buries every one of his enemies, but crap fantasy can't really be held to the same rules that good fantasy can be, right?
Your post interested me because I'm writing a story - not fantasy, sadly - about a post-Apocalyptic world where a killer virus has ravaged the earth. The protagonist - an anti-hero - lives with about 1,000 others in a secluded compound which she helps lead. There is one situation where a man comes in from the outside and does not appear to have the virus. However, instead of being hospitable, she takes him into interrogation, tortures him, and then, when he doesn't have any useful information, throws him back out into the Outside. It isn't meant to be melodramatic, or create sympathy for the character in question - none of the, "Oh, but she is a tortured soul and was confused about what to do!" She just did it because it made the most sense - "It seemed like a good idea at the time," as a character from your story would say. I think that defines an anti-hero: someone who does not let moral inhibitions stop them from what they think is *smart*.
Well, /rant. Thanks for putting up with it!