Real Name: Hino Rei 
Name meaning: spirit of fire 
Birthday: April 17th 
Zodiac Sign: Aries 
Height: 5'3" 
Senshi Position: Inner Senshi
Element: fire
Fighting Style: offensive
Secret Weapons: being a Shinto priestess
Favorite Color: red, black 
Hobbies: fortune telling, reading 
Favorite Subject: Ancient writing 
Worst Subject: Modern society 
Favorite Food: fugu 
Favorite Gemstone: ruby 
Family: her mother is dead, her father is alive but she lives with her grandfather 
Dream: to be a Shinto Priestess, a singer, and a model 
Seiyuu: Tomizawa Michie 

Rei is very strong-willed and ambitious. She is the senshi of fire, and her personality basically matches her powers. She is very spirited and opinionated. She has a hot temper and is aggressive, usually rushing right into a fight without a second thought. She's also extroverted and tends to say things without a second thought as well.
Rei goes to TA Academy, which is a girls' school and Catholic also, even though she's not Catholic, she's Shinto. Her dad just wanted her to go there, I guess, so she'd get a decent education (my situation exactly!). She's basically the queen of her school. Everyone there treats her like she's some kind of goddess. And of course she laps up all the attention. She loves the spotlight, and likes to sing as well. She wants to be a model, singer, or seiyuu when she's older, probably because she'd be rich and famous and get lots of attention. She has no shame in self-promotion, and she dedicated her school's culture festival almost entirely to her and her songs. Well, at least she has a healthy ego.
Her mother died when she was very young. Instead of living with her father as she should have, she preferred to live with her grandfather at the Hikawa Shrine because her father was a politician and never had enough time for her. Her ojii-san (grandfather) isn't the most virtuous old guy. In fact, he's a complete pervert. There are even warnings posted in the newspaper for young girls to stay away from their shrine because of him. But Rei prefers to live with him instead of with her apathetic father.
Rei's psychic abilities make it hard to sneak up on her. She can sense when something bad is happening or is about to happen. She can also do fire readings, where she asks the sacred fire at her temple a question and...well, I guess she reads the fire for an answer (I'm not too sure exactly what happens). She also carries around little scrolls called ofuda, which have "aku ryo tai san" (evil spirit, begone) written on them in Japanese. She chants with the ofuda in her hand and then says "Akuryo Taisan!" and throws it.
If Rei really cares for a person and likes them a lot, she'll treat them badly. It's just one of those weird things she does. Usagi is the best example of that. At first Rei disliked Usagi and was sick of her whining all the time. But she actually cares greatly for Usagi (she even addresses her without an honorary like "Usagi-chan" or something, which shows her closeness to Usagi). The only reason she's mean to her is because she aspires for Usagi to work to her full potential, or something like that, and if yelling at her occasionally will get Usagi focused, Rei will do that. Sure, she comes off as a bitch, but it's just how she operates. Same thing with Yuuichirou, the guy who works at her shrine. He honestly loves her, and he'd do whatever he had to to help her if she were in trouble (see the ski lodge episode). He even threatens Haruka when he thinks that Haruka is cheating on Rei with Michiru. ^-^ But Rei usually treats him badly and pushes him away, even though she also cares for him. It's just a thing that she does, but nonetheless, she's still popular at school. 

Mars Power, Make-Up
Rei says this to turn into Sailor Mars in the first season.

Mars Star Power, Make-Up
Rei says this to turn into Sailor Mars in R on.

Mars Crystal Power, Make-Up
Rei says this to turn into Sailor Mars in SS on.

Fire Soul
Sailor Mars says this and puts her hands together, and she creates a fireball that she directs toward her enemy.

Akuryou Fuji no Ofuda
Rei or Sailor Mars chants on a ward (those little pieces of paper with writing on them that she always has).  Then she throws this at the back of the monster's head, yelling "Akuryou Taisan!"  The ward stuns them or even drains them of their evil.

Fire Soul Bird
Same as Fire Soul, only the fireball turns into a bird that flies toward the enemies.

Burning Mandala
Sailor Mars says this and rings of fire circle around her.  She then can direct the rings toward her enemies.

Mars Flame Sniper
Sailor Mars says this and a red arrow forms in her hands.  It forms a red bow and arrow, and Mars can shoot the arrow at her enemy.

Henshin pens
3 different ones: the first one, the one she gets with her R power-up, and the one that turns her into her super form.

A communications device that is disguised as a calculator that all the senshi have.

Communicator watch
A watch that sort of takes the place of the communicators that all the senshi get in R.
The scroll that Rei/Sailor Mars has that she can use with her Akuryou Fuji no Ofuda attack.