Major Clanger kindly links to a new set of interpretations of these basic types...
ISTP: The Psycho Vigilante
ISTPs are quiet, unassuming people, who tend to be mechanically gifted but withdrawn and reserved. ISTPs often need a great deal of personal space and "alone time," which may give others the impression that they are aloof; in reality, this time is necessary to hide their secret identities. [snip] Romantic relationships with ISTPs tend to be drawn-out, tragic affairs, filled with bitterness, longing, and teenage angst. The sex is usually pretty good, however.
Famous ISTPs include Spider-Man and Q.
Sometimes I'm an ISTJ instead, usually when I've been hunting down and executing spammers.
ISTJ: The Thought Police
For an ISTJ, work is very important to a sense of self-satisfaction. [snip] you're most satisfied when you are crushing the population beneath the iron boot heel of oppression on behalf of your masters.