It can be useful – no essential – to find out who you are so you can market your uniqueness.
Career and personality assessments are a great way to go.
Online, short assessment to determine personality type according to Jung and Meyers Briggs’ psychological research.
Temperament Sorter – based on Meyers Briggs. Free assessment plus more complete report at reasonable cost. Keirsey is very well regarded.
Now, Discover Your Strengths: Marcus Buckingham & Donald O. Clifton
This book explains Gallup’s Strength Research. Includes access code to online assessment of your own strengths.
Buy from any bookstore or online.
Emotional intelligence is a fairly new area for analyzing your personality and leadership skills. This site has a reasonably priced assessment.