There are number of possibilities that spring to mind for a variety of reasons.
First up is Noa Izumi from Patlabor. One of the things that makes Noa one of my favourites is that she works for her skills. Yes, there's a lot of natural talent there, but there's also the lady who in any other world would have a perpetual grease stain on her cheek because of the time spent tinkering under the hood of a car. The dedication and hard work is so convincingly presented, particularly in the TV series, that you can't help but respect her achievements.
One of the stronger aspects of the TV series comes on those occasions when Noa doesn't realise just how good she's become. The shock and disbelief when she realises that someone is attempting to head hunt her from SV2 is convincing, and something that many people will relate to.
Second is Hikaru Shidou from Magic Knights Rayearth, particularly in the first season. This is one of CLAMP's earlier, and stronger, series and Hikaru is a classic example of a heroine on an epic scale, triumphing through pure willpower. I do have to admit that whilst Hikaru grows in power through the series there isn't that much character development as such (and to an extent this is true of all the three major characters in Magic Knights Rayearth). Don't get me wrong, I adore this series but it does have some problems with characterisations (Gimme the brain cell, I need it this episode!).
Which is why, in the end, I have to go with the third possibility that immediately springs to mind: Hitomi Kanzaki from the Vision of Escaflowne.
As I mentioned when I selected the passing of the Fortune Twins for the saddest scene, Hitomi is a character who is forced to grow up, to become an adult, by the events she has to deal with in the storyline. Her characterisation is very real, there is a lot of attention to detail in her physical abilities (justified as an athlete), and the her actions have real consequences that she has to learn to deal with.
There is fear to be faced, and in dealing with the fear there is courage, heroism, and responsibility. Oh, and the occasional dash of romance. :)
Day 1 - Very first animé: Robotech, Gall Force, Vampire Princess Miyu.
Day 2 - Favourite TV series: Card Captor Sakura.
Day 3 - Your animé crush: Oh grow UP already.
Day 4 - Favourite Film: My Neighbour Totoro.
Day 5 - Animé character you feel you are most like (or wish you were): Kinoshita, Rocket Girls.
Day 6 - Most annoying animé character: Lynn Minmei, Super Dimensional Fortress Macross.
Day 7 - Character you’d most like to slap: Hiyama Hikaru, Kimagure Orange Road.
Day 8 - Most epic scene ever: Launch day - Wings of Honneamise.
Day 9 - Saddest animé scene: The passing of the Fortune Twins - Nariya and Eriya.
Day 10 - Favourite slice of life animé: ARIA.
Day 11 - Favourite mecha series: Patlabor: The Mobile Police.
Day 12 - Best instalment of a franchise you don’t like: Mobile Suit Gundam 0080: The War In The Pocket.
Day 13 - Worst instalment of a franchise you do like: WXIII: Patlabor the Movie 3.
Day 14 - Current (or most recent) animé wallpaper: I think I had a Silent Mobius wallpaper once.
Day 15 - A reality check for a genre you like: Romantic/Heroic Space Pirates.
Day 16 - An animé classic that simply doesn’t work for you: Ghost in the Shell (film).
Day 17 - Best Background Music: Silent Mobius 2: The Motion Picture.
Day 18 - Best Five-team: Silent Mobius.
Day 19 - Change you’d like to make to any one animé: Add an animation budget to Lodoss Wars.
Day 20 - Most ambiguous animé character: Reki, Haibane Renmei.
Day 21 – Favourite OAV Series: El Hazard the Magnificent World.
Day 22 - Animation studio you'd most like to slap: Gainax.
Day 23 - Animé you think had the best, or most intriguing art: Reki's paintings in Haibane Renmei.
Day 24 - Favourite animé hero or heroine: Hitomi Kanzaki, Vision of Escaflowne
Day 25 - Best animé villain
Day 26 - Your favourite harem animé
Day 27 - Favourite animé opening theme song
Day 28 - Favourite animé companion/summoned creature
Day 29 - Best Animé Music Video
Day 30 - Favourite animé ending theme