"Beneath the quiet exterior, INFJs hold deep convictions about the weightier matters of life. Those who are activists -- INFJs gravitate toward such a role -- are there for the cause, not for personal glory or political power.

INFJs are champions of the oppressed and downtrodden. They often are found in the wake of an emergency, rescuing those who are in acute distress. INFJs may fantasize about getting revenge on those who victimize the defenseless. The concept of 'poetic justice' is appealing to the INFJ.

Accurately suspicious about others' motives, INFJs are not easily led. These are the people that you can rarely fool any of the time. Though affable and sympathetic to most, INFJs are selective about their friends. Such a friendship is a symbiotic bond that transcends mere words.

INFJs have a knack for fluency in language and facility in communication. In addition, nonverbal sensitivity enables the INFJ to know and be known by others intimately.

Writing, counseling, public service and even politics are areas where INFJs frequently find their niche."

"ENTPs are energized by challenge and are often inspired by a problem that others perceive as impossible to solve"

Check.

"They are confident in their ability to think creatively, and may assume that others are too tied to tradition to see a new way"

Check.

"ENTPs are masters of re-inventing the wheel and often refuse to do a task the same way twice"

Check.

"ENTPs are usually very intelligent, but since they are naturally rebellious, don't do well in school or other rigid settings"

Check.

"It can fall painfully flat when an ENTP steps on someone’s toes by say, openly questioning their boss in a meeting, or picking apart everything an authority says."

Just described the reason why I got into 65% of the trouble I had in my life, though nowadays I try to control it.

"For the ENTP, the rules of the universe are made to be broken"

This can be kind of true.

"... the haunting sense of impending failure..." Yep. That's a check.

"Mathematics is a system where many INTPs love to play, similarly languages, computer systems..." I love maths and learning new languages and computers... Another check.

"One of the tipoffs that a person is an INTP is his or her obsession with logical correctness." I've had my classmates turn exasperated at me because of my 'logical correctness'.

"Games NTs seem to especially enjoy include Risk, Bridge, Stratego, Chess, Go, and word games of all sorts." ... I like playing chess (and the very few word games I've played) a lot.