Hino Rei is a maiden (miko) at the Hikawa Jinja temple. She was the second senshi to join with Sailormoon. She goes to the private T*A girls school (a very prestigious school). Rei is very spiritual and she is psychic. She is usually the one to say if there is an evil prescence around. Rei will not hesitate to throw her ofuda on people (as seen on the episode when Usagi met Rei for the first time) The ofuda is a piece of paper that Rei uses to banish evil spirits. Rei kinda has a boyfriend named Kamada Yuuichirou. He's a sweetie but he doesn't really know how to express his feelings for Rei. Rei is also guarded by her two crows, Phobos and Deimos. In the manga, they can turn into sprites. (little people) They helped to power her up to Super Sailor Mars in the manga.
As Sailor Mars, she has fire based attacks. She is also the strongest of the Inner Senshi, power wise. Her first attack is the Fire Soul. The Fire Soul shoots flames at an enemy. Her second attack is the Fire Soul Bird, which is a powered up version of the Fire Soul, the only difference that it is in the shape of a bird. The Burning Mandala is her third attack that she got in the second part of the R series against Cooan. (It set her tutu on fire ^_^) It shoots rings of fire at the enemy. In the SuperS series when she is powered up to Super Sailor Mars, she gets the attack Mars Flame Sniper. It is used like a bow and arrow. In the manga, Rei is very talented at archery, so that's why her attack is a bow and arrow. 
Also in the manga, Rei has the attack Mars Snake Fire. It a a jet of fire in the shape of a snake head. She used this attack against Eudial in the manga.
Rei can often be found bickering with Usagi. Because of that, a lot of people think Rei hates Usagi, but that's really NOT true! Actually, Rei is probably the closest to Usagi. When Usagi really needs her, Rei will always be there for her. Like in the R movie, who was sitting next to Usagi when she thought Mamoru was gone? There are a lot of little instances that shows you how close Usagi is to Rei.
Hino hoshi kaseio shiyugonimotsu tatakai no senshi, Sailor Mars! (I am the soldier of war, and I carry the protection of the planet of fire, Mars. Sailor Mars!)
My Opinion: I love Rei! I think she is very misunderstood! Sure sometimes she's hard on Usagi but she IS Usagi's best friend. What would the senshi be like without Sailor Mars? She is very powerful and how can you not like fire? 'nuff said!