I was tempted, briefly, to pick Grospoliner, The Emperor of Swords (literally) from Silent Mobius but I don't think he really fits the spirit of the question.
However there's a companion to a magical girl that fits the bill perfectly for me: Kero-chan from CardCaptor Sakura.
Alternating cute with annoying, Kero-chan has enough idiosyncrasies to be a fully realised character in his own right.
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: Nakago, Fushigi Yugi
Day 26 - Your favourite harem animé: Ouran High Host Club
Day 27 - Favourite animé opening theme song: Adesso E Fortuna, Record of Lodoss Wars
Day 28 - Favourite animé companion/summoned creature - Kero-chan, Card Captor Sakura
Day 29 - Best Animé Music Video
Day 30 - Favourite animé ending theme