A few notable Force-users have wielded purple lightsabers, though they were mostly Jedi. Most notably we have Mara Jade who used a magenta lightsaber. She was once Emperor Palpatine's right hand until she defected and eventually married Luke Skywalker. And of course, Mace Windu was the most famous Jedi to use a lightsaber with purple blade, and he was known for his strong will and occasionally volatile temper.

The purple lightsaber was a sign of someone who used both the light and dark sides of the force, as purple is a combination of the colors blue (typically used by Jedi) and red (typically used by Sith). Mace Windu is a perfect example of this as he would channel his fury to accomplish great feats on the battlefield without ever giving in to his emotions completely.

Mace Windu was one of the most powerful Jedi Masters to ever live. His mastery of the force and his prowess with a lightsaber were nearly unrivaled. Mace Windu invented a new form of Lightsaber combat called Vapaad, which channeled the user's passionate emotions without giving in entirely to the dark side. This allowed him to hold his own even against Sidious, the Lord of the Sith.

The most likely scenario where you would use a purple lightsaber is if you are a Grey Jedi who balances light and dark force tendencies. Meditate with the force and decide if you wish to walk the path of light, the path of dark, or the middle way.

Mace Windu had special talents and abilities that no other Jedi could master, and that is part of what made him so formidable on the battlefield. He was the only Jedi to best Darth Sidious in combat. With years of dedicated training, it may be possible to become as powerful as Mace Windu, but don't get discouraged if your progress is slow--most Jedi never attain the rank of Master.