Hero of JusticeFollowing in the footsteps of Mami, her mentor, Sayaka also believes it is the role of a magical girl to be a defender of justice. Magical girls hold the responsibility of protecting the town from witches and familiars. Saving people should be their number one priority. After Mami's death in the main timeline, Sayaka is concerned about what will happen to their town because she realizes their way of thinking is different from other magical girls. She is skeptical that if another girl moves in, she will be more concerned about grief seeds than actually saving people. Although Sayaka does primarily become a magical girl for Kyousuke's sake, her decision is also in part fueled by her desire to prevent such a magical girl from moving in. In the PSP game, Sayaka states that a big part of why she became a magical girl was to protect the town from witches. She wanted to save those who couldn't defend themselves because their threat is invisible to normal people. Sayaka even goes as far as telling Madoka that she will protect the town in Mami's place. Therefore, Sayaka believes it is her duty to fill the role that Mami held before she died. She truly fights single-mindedly for the sake of others.
Unfortunately, Sayaka's sense of justice is absolute in her mind. She has very black and white thinking when it comes to saving others and being an ally of justice. A magical girl must save and protect everyone. A magical girl must keep fighting until she prevails because the lives of others are on the line, even if that means risking her own safety. A magical girl always thinks of others before herself. While Sayaka's beliefs are admirable, they create both unrealistic expectations for herself and lead to conflicts with others. A big part of her eventual despair in multiple timelines is because she feels she doesn't represent these ideals all of the time. Further, Sayaka puts herself in danger by refusing to back down in her beliefs around this subject, both in confrontation with Kyouko and by refusing the help of Kyouko or Homura. Sayaka is absolutely enraged to hear Kyouko talk about how people are part of the food chain in relation to witches and how she's stupid for trying to fight with a familiar when you can't get grief seeds from them. Sayaka is clearly no match for Kyouko's skill and experience. Even so, she stubbornly refuses to back down and is willing to fight to the death in order to stand up for her beliefs. Her requirement of magical girls being selfless all the time creates a rift between her and Kyouko and thus causes her to decline Kyouko's help in battle (and therefore pushing herself past her limit) as well as not using grief seeds from Homura or Kyouko despite her soul gem being tainted.
I have no doubt that Sayaka's desire to protect others is real. Right from the very beginning, Sayaka positions herself in front of Madoka to protect her from Homura as well as try to protect her from their first witch encounter. She is also willing to put herself in danger by staying with the soon-to-hatch grief seed in order to protect the hospital and Kyousuke. However, Sayaka also seems to view (probably unconsciously) being a magical girl as a way to feel a sense of accomplishment and being needed. Kyouko is able to prevent Sayaka from despairing in one route of the PSP game by reminding her that the people of the town need her. Even if they don't know what she is doing for them, they need someone to defend them from the threat they can't see. Sayaka cries because she is happy that she isn't worthless and that people do actually need her to be around. Also, she tells Madoka that she feels a great sense of accomplishment from protecting the town in the Vita game. It would seem Sayaka really feels that being a magical girl is her purpose in life. This accomplishment, pride and purpose is enough to keep her moving forward despite everything else going on around her that causes her to despair in other timelines. Sayaka really assimilates being a magical girl—an ally of justice—into her identity.
Sayaka's MagicEach magical girl has her own type of magic that depends heavily on the wish she contracted for. Sayaka's strongest type of magic is regeneration, which really isn't surprising since she wished for Kyousuke's hand to be healed! Her body heals twice as fast as a normal person. Sayaka is able to get back up and keep fighting despite being knocked down hard because of this. For example, when Kyouko uses an attack that should have knocked her out of commission for at least three months (or so she says, anyway), Sayaka manages to get back on her feet moments later. Flesh wounds are healed quickly by rings of music notes, too. While Sayaka's regenerative abilities generally seem to only apply to herself, she is shown healing a badly injured Mami in The Different Story timeline. So, perhaps with more experience and guidance like she had in that timeline, Sayaka would have the ability to heal others as well.
Sayaka's offensive magic takes the form of a cutlass. She typically uses it as a melee weapon—basically hacking and slashing until she wins. However, Sayaka is also able to summon multiple swords at once and throw them individually or send them all flying at the enemy! She doesn't have a "final" attack like Kyouko or Mami, but in Hangyaku no Monogatari, she uses an attack called "The Five Lillians," in which she throws five swords at the Nightmare. I've tried to do some research into the significance of the name, but didn't find anything that seemed relevant. However, the name Lillian is French for "lily." Lilies usually represent purity or innocence. So, perhaps the attack could represent the loss of the Holy Quintet's innocence. They were just ordinary girls before making a contract. Arguably, either through the reason behind their contract or after becoming magical girls, all five of them lost their innocence and became fighters. Perhaps "lilies" being used as an offensive attack could symbolize this evolution. I personally feel Sayaka's story and character represents what happens to magical girls (moving from hope to despair, finding out the truth about soul gems, etc.), so it could make sense that this attack symbolizes the five of them!
I think having a cutlass for a weapon is very representative of Sayaka's personality as well. Characters who have swords are usually the brave, courageous, reckless and impulsive heroes, after all. As I've mentioned in a number of places on this site already, those are among her strongest personality traits. Further, Sayaka's fighting style relies heavily on charging in and fighting the enemy at close range with everything she has because she isn't as strong or experienced as the other magical girls. She even admits that she doesn't have any natural talent for fighting, either. Despite this, she still gives it all she has because she wants to protect other people. This mentality as well as her shortcomings in battle remind me of a typical protagonist with a sword. I'd have a hard time imagining Sayaka using any other weapon because of her personality and the way she fights. She's certainly not one to consider a strategy or look for weaknesses in her enemies like Homura or Mami. Sayaka's fiery personality seems to be best suited to a weapon like a sword.