I think that personality theories are somewhat pseudo-scientific and should be explored lightly, but I do view them as useful tools for personal advancement and psycho-social understanding. While I feel that theories discussed here have potential to be used in egotistical ways that may be psychologically damaging, I think that the Enneagram is useful in identifying the motivations and poisonous thoughts (as a key founder stated them) that drive people and are particularly helpful for spiritual :P advancement, but in a less concrete way as explained by the overall theory itself, and that the MBTI is valuable in identifying how people interact and view themselves socially. Individuals are immensely more complex than can be explained by a central instinct/fear or guiding 'cognitive function'. Although they should be taken lightly, I do think theories such as the MBTI, Socionics and the Enneagram are nonetheless useful as indicators of personality and (more importantly) as methods of understanding psychological problems, and I am grateful that places like personalitycafe exist as open and understanding arenas of exploration in the human psyche.  
Nonetheless:
Enneagram: Either 5w4 or 7w6 core, followed by 1w9 and 4w3 in preference
Cognitive Function test results:
Ni - Fe - Ti - Fi - Si - Ne - Te - Se
missjayjay Perspicacious Raain Wake