1.) Soi Fong does not like to shave her legs. Still, she does it because if there's something she learned from her erstwhile mentor slash god-figure, Shihouin Yoruichi, it's that if you murder someone, you had better look good while doing it .
2.) She loathes her lieutenant. She knows that he is capable - family connections or not, one does not survive in the Second without some punch to back up a big mouth - and that he is an awesome way to get some free time by making him do all her paperwork, but he is an arrogant, overbearing, misogynist ass who dares to spread foodcrumbs on her head. She does NOT need a reminder that she's tiny all the time.
3.) In the same vein, while she fears no captain of the Gotei 13, she is highly uncomfortable around both Komamura Sajin and Zaraki Kenpachi. Not because each of them could kill her in one hit (after all, they'd have to CONNECT for that to happen, and she's so very, very fast), but because both of them are absolutely huge, gigantic walls of muscle.
4.) She really likes to have free time. It has been a century since she has been nothing more than a duty-bound half-slave. She is a duty-bound captain now, and with that rank and her power come a lot of privileges. For someone who never had any before, it was an awesome experience. And Soi Fong, as the head of the Special Forces, has unparalleled access to the living world. There are so many, many, many things a young woman can do in the living world, Soi Fong has found out. And most of them are great fun.
5.) She has never understood the hubbub some people make about sex. Raised, no, born to serve, the woman that later became Captain Soi Fong of the Second Division has the sex drive of a particularly lifeless patch of moss, and since she can't see anything wrong about it, is entirely unwilling to change this.
6.) Soi Fong is second only to ex-Captain Ichimaru in the ability to break people through torture. However, where Gin does it for fun, she does it because someone has to. And she can control her zanpakuto's ability to "kill". Most traitor-shinigami and hollows tend to break after watching one of their limbs fight and lose to spiritonecrosis, after all.
7.) Soi Fong likes to play darts. Soi fong likes to play darts so much, in fact, that she always insists on doing so when she gets the chance to do it - and that's pretty often, in Seireitei - that there is a long-running betting pool on when she'll miss hitting at least one perfect bullseye out of three throws with any sufficiently aerodynamic projectile (including Captain Zaraki, who really got a laugh out of the "angry lesbian shrimp throwing me around like that")
8.) Contrary to very, very popular opinion, Soi Fong is not a lesbian. She would be shocked and mortified at the amount of lesbian pornographic art featuring her (and, in most cases, Yoruichi), and quick to punish the fool peddling it. She has never had any interest in women, but the same is true for men.
9.) Suzumebachi is an extension of herself, literally. Her shikai takes away any and all defensive capability her sword possesses for nearly unmatched killing power. Soi Fong is a glass cannon, even though that glass is hardened beyond all imagination through training, will and furious determination.
10.) She is gravely wounded during the last battle of the Winter War. When her Hollow side is empowered by the acts of the arch-traitor, her worst aspects take over, and she goes on a rampage. She finds many of her own division to be unworthy of existing, of being an affront to her senses, to be guilty because they are -weak-. Soi Fong, in a demonically-fuelled judgement spree murders, within five minutes, sixty percent of her division. While she is judged innocent by her peers, what really haunts her, even years later, is that she -still- does not feel remorse for doing it.
11.) After the Winter War, her relationship with Shihouin Yoruichi is strained to the point of a half-dozen closely averted catfights. Soi Fong loves her former teacher/mistress/god-figure/surrogate mother-figure to pieces, but she desperately feels that she must be herself... even though she does has no idea what being Soi Fong should be like.
12.) She is one of those people in Soul Society willing and ready to call Kuchiki Rukia on her abysmal failures at drawing cute animals. Like all the others who do so, she is powerful enough to evade the wrath of the Kuchiki heiress, but unlike the others, Soi Fong, through years of drawing images used in investigations, is a master-class artist willing, ready and able to draw another volume of Usagi Shinigami. Rukia would be horrified to know that she tried to raise her hand against the creator of Seireitei's most popular comic.
13.) She believes in regular exercise and a controlled diet to keep fit, but completely overshoots her self-set goals. It's something she has in common with Hitsugaya Toushiro, another firm believer in extensive self-training. Neither of them, under pain of torture and death, would ever admit that they themselves might be the reasons why they are so short. Both of them had a troubled youth and neither is willing to grow up, for reasons entirely too similar.
14.) Soi Fong enjoys reading cliched action novels. One day, she swears, she'll get a piranha pitfall trap installed in front of her office desk, and another one in front of her office door. If someone is serious about disturbing her, they'll find means to get past the security. If not, well, they get eaten by ferocious fish, which is just as well in her books.
15.) She is the best martial artist in all of Seireitei, including the wayward Shihouin princess. While her erstwhile lady is quite a lot more skilled than Soi Fong in all things reiatsu manipulation, in pure hand-to-hand, Soi Fong stands supreme.
16.) In her gloomier moments, Soi Fong finds herself stealing things from her fellow shinigami and expertly placing the blame on others. Watching events unfold (and, if necessary, breaking up any fights) could be called one of her hobbies, if Soi Fong would admit to herself that she has any.
17.) One day, Madarame Ikkaku decides to test his mettle against speed, not brute force. While Soi Fong makes quick work of him, she finds that getting him to stay down is a lot harder than it appears to be. Ikkaku, on the other hand, is determined not to stop fighting her until he can actually block her strikes. To their mutual horror, they find out that love can bloom on the battlefield.
18.) She likes to teach Martial Arts courses at the shinigami academy. Not only does she get a decent workout from holding herself back instead of ripping the students to pieces, but she really, really enjoys the excited looks on the faces of some of those who spar against her. Soi Fong, for all her stern, dry nature, has the least problems of all captains with recruiting prospective shinigami into her division.
19.) What most people do not understand when they see her is that Soi Fong is a captain. They compare her with Ise Nanao, who is just as stern as Soi Fong. They compare her with Kuchiki Rukia, who is just as short and just as violent. They do not, however, compare her with Zaraki the Berserker, whose battle-fury she can match, though not exceed, nor with Kuchiki "Kinslayer" Byakuya, whom she shares a sobriquet with - "Executioner". Too late and to their sorrow do those who underestimate the fury of bankai realize their fate when they engage Soi Fong.
20.) Soi Fong is always ready to kill her fellow Shinigami if they turn traitor. She knows she and Suzumebachi are made for this. In some nights she wonders, though, if she is the knife in the darkness that ends treason - or rather, should end, given her abject failure to deal with the Arch-Traitor and his ilk - whose hand is it that points a knife at her heart? Then she closes her eyes and knows that she will serve Seireitei until her dying day anyways... whether from old age, or because someone mercykills her.