Akira Ishida plays either effeminate and/or gay male characters fairly frequently, a role usually given to female voice actors, or villains. For the former, this seems intentional, as many of his roles even look similar physically.
Mostima is, so to speak, a literal "Dark" "Magical" girl, but not a Dark Magical Girl, being more of a lone wolf, and a very casual and relaxed character.
His 'interact with girls younger than his character' is also very much seen in Gundam 00, as Big Brother Mentor Lockon Stratos interacts a lot with Emotionless Girl Feldt Grace. The catch is, instead of Lockon being interested at her, it was Feldt who ends up having an unrequited crush on him.
Hikaru Midorikawa's most common roles are quiet, antisocial bishounen types. However, in the Banpresto multiverse, he's cast as a loud-mouthed ignorant jock of a character. In one of the "Preview of Next Episode" savescreens, he imitated Heero Yui, a more standard Midorikawa Hikaru role, and confused everyone.
If anything, anyone voiced by Midorikawa will usually have an air of 'coolness' around him, something that is exploited to hell and back in Haven't You Heard? I'm Sakamoto. Cool, Cooler, Coolest indeed.
Expect almost any characters played by Ayako Kawasumi to have a 'dark side'. It happened many times... First, her character in Gate Keepers Ruriko Ikusawa had her powers converted to the dark when she's kidnapped, second, Chikane Himemiya in Destiny of the Shrine Maiden snaps and converts a Mecha into evil while submitting to a dark god, though to be honest, it's just a huge Gambit Roulette to her, and lastly one of the routes in Fate/stay night had Saber get defeated and turn to... Saber Alter.
Nobuyuki Hiyama has a lot of range from deranged villains to cool and calm characters, but thanks to his role as Guy Shishioh, and Breakout Role as Hiei, fans noted that his common roles are hot blooded characters. He is also notable for being the "voice" of Link in Ocarina of Time.
Junko Takeuchi, thanks to her role as Naruto, has been often typecast as goofy young boys such as Hokutomaru in Garou Mark of the Wolves, Dieter from Monster, Gon Freeces In Hunter × Hunter, and Mamoru Endou in Inazuma Eleven.
Yuu Asakawa. It's not seldom that she'll play characters who are the most well-endowed between the cast, thereby turning her to be the candidate of the series' Ms. Fanservice. If the series is full of Ms Fanservices already... let's just say she'll be one of the top Fanservice providers.
Then there's Joseph Joestar, who not only weaponizes his snark but manages to be a Large Ham at the same time.
Ryūsei Nakao has been typecast as cruel, quirky, disturbing, sadistic men (mostly villains) with high pitched voices, including Freeza (and his brother, Cooler, and his counterpart, Frost), Mayuri Kurotsuchi in Bleach, Him in Powerpuff Girls Z, Caesar Clown in One Piece as well as Farfarello.
Voice actress Yuki Kaida has been more or less typecast to play soft-spoken teenage boys with hidden agendas or skills, like Shusuke Fuji from The Prince of Tennis and Kurapica from Hunter × Hunter (whom she even plays in the musicals). One of the few different roles she has been casted as is the gentle and troubled Machi Kuragi in the Fruits Basket CD-dramas.
Yūko Gotō often plays girly Moe characters like Mikuru from The Melancholy of Haruhi Suzumiya. Ironically, Goto (aka "Gotouther-sama" after a character from Fist of the North Star, of which she is a fan) is apparently a hardcore biker in real life. Parodied in Lucky Star, in which she appears as an intimidating, hypermasculine Yakuza-style biker, then zooms off on her motorcycle making cutesy "vroom, vroom" noises.
However... it seems she is set to not only Moe characters, but also Yandere characters. If Kaede Fuyou is telling you something...
If you want a good seiyuu for a female character older than 30? Go to Masako Katsuki. She started with Naïve Everygirl (like Maya Kitajima form Garasu no Kamen) or Cool Big Sis (like Reccoa from Zeta Gundam) roles, but ever since she played Michiru aka Sailor Neptune in Sailor Moon she's been playing older ladies.
She played some older ladies before that, too; take Ikari-sensei from High School Kimengumi in the 1980s.
Fumihiko Tachiki is well-known for his work voicing sinister older villains, who usually share very personal connections to one or more of the main characters. This also usually goes hand in hand with his roles' tendencies, if they have children, to be at best distant or at worst downright manipulating and bad fathers. Most famously, of course, is Gendo Ikari from Neon Genesis Evangelion, but he has also played Kratos Aurion from Tales of Symphonia, Odin from Odin Sphere and Zaraki Kenpachi from Bleach. And even young comic relief Boss from Mazinkaiser. To sum it up, he's a very good choice for Big Guy type of characters, even moreso if they have a veteran-ish aura.
George Nakata = Villain. That's all that needs to be said. Granted, some of those villains are also protagonists, like Alucard in Hellsing, but villains nonetheless.
Hideyuki Hori, though not as much as obviously seen, seems to be a rather popular choice for ninja characters. Including Ryu Hayabusa in Ninja Gaiden and Dead or Alive, Schwarz Bruder in G Gundam, and in the crossover Namco X Capcom, he plays Team Commando's resident ninja Sho/Ginzu.
If you see Show Hayami's name in a cast list, take extra caution. If that character seems like affable and attractive, there is a chance that he'll turn out to be the worst man in existence (case in point, Dr. Kazutaka Muraki in Descendants of Darkness, Masami Eiri in Serial Experiments Lain, and Sousuke Aizen in Bleach). He also plays straight socio/psychopaths just as often.
She can also play screwball characters, as she played Woody Woodpecker in the dub of his 90s TV series.
Yūichi Nakamura tends to play guys who, for a lack of better description, are jerks. Usually with hearts of gold underneath. We have Okazaki Tomoya from CLANNAD (a jerk who quickly softens up for his various love interests), Abe Takaya from Big Windup! (a jerk who doesn't realize that yelling at his shy, meek pitcher isn't helping said pitcher's self-esteem any), Alto Saotome of Macross Frontier (a jerk who has trouble recognizing other people's kindness toward him, especially if they happen to be his love interests), Ikuto Tsukiyomi of Shugo Chara!, etc. Meanwhile, Yuuki Terumi takes this pidgeonhole to psychopathic levels.
At the same time, Nakamura also played a noticeable number of times fathers and especially olderbrothers (or even younger brother in Wata Mote), which is characteristic, the latter predominantly in Brother–Sister Incest series or playing with this. Put a plus if in a similar work also plays Saori Hayami as one of his Love Interest.
Thanks to his role as L from Death Note, expect him to also play emo-ish characters like Cheshire or Feitan.
He does quite well with goofball characters as well. Want an example? How about Teddie? Or Shigechi? Could Bugs Bunny count?
Hitomi Nabatame is a versatile voice actress, doing stuffs from young girl, graceful princess, outgoing girls or characters. However, if there's several things she's most known for, it's either her Hard-Drinking Party Girl roles, or roles that have Les Yay painted in it. She may be even like this in real life.
Sometimes, a voice actor is pigeonholed into one type, but as time passed on, he/she is pigeonholed in another type and almost abandons their old pigeonholed types. The example of this is Aya Hisakawa, known as young, mostly spunky girl characters, especially Ami Mizuno/Sailor Mercury, Skuld, and Chai Xianghua. But as time passed, she finds herself pigeonholed into mature women that knows her stuffs, such as Maya Natsume, Retsu Unohana or even StripperifficMs. FanserviceJudith. This is also somehow reflected in her old pigeonholed types — one of the Ah! My Goddess series features Skuld with an older form, and Hisakawa left Xianghua's role after Soul Calibur III.
Natsuko Kuwatani is mostly known for absolutely loyal henchwoman to whomever she works for rather then the actual cause her master follows and rarely cares for anybody else. Kasuga in Sengoku Basara, Sette and Arf in Nanoha are good examples of following her master to the ends of the earth and often hints of a romance of them (some more blatant then others). Just call her Natsuko Kunoichi in that case.
Shizuka Itō is known for her refined sexy personality (she does do hentai after all) and is often seen working with girlfriend Hitomi Nabatame (they have a good relationship, and apparently they are girlfriends if Hitomi's blog is to be believed) and the ability to go between romantically teasing or generally stoic and serious. Rest assured, she is a skilled femme fatale who is on fire (or at least her element in animes like Shakugan no Shana). She is also typecasted in high school anime as a Student Council President or representative.
Soichiro Hoshi is often the younger partner of Akira Ishida. Aside from that, he plays normally passive characters with hidden berserker streaks to him such as Kira Yamato from Mobile Suit Gundam SEED franchise and Brooklyn from Bakuten Shoot Beyblade. His roles often carry sticks or similar stick-like weapons to battle. Beamspam Jesus has nothing on stick smack Jesus.
Kazuma and Keiichi Maebara may be considered inversions. Both definitely have berserker sides to them, and Keiichi has a baseball bat as a weapon but Kazuma is openly loud, brash and violent while Keiichi is a loud, perverted dork who only becomes violent when he falls victim to the Hate Plague.
Ditto Masaru, who is made of hot blood and punches out fifty-foot giant chickens in his spare time. And Sanada Yukimura is basically the former dialed up to eleven.
Mitsuki Saiga mainly plays male roles despite being a female seiyuu. Many of the roles she plays is mainly as protectors but when she also has to play a villain as well, it becomes a Well-Intentioned Extremist character. Example is Makubex from Get Backers. And if she doesn't play boys, she plays Action Girl types, like Jun from the Mazinkaiser OAV.
Marina Inoue when doing major roles is mostly cast in the Ojou role most of the time. While not always of the lady in fine dress theme, there is a generally air of being a woman with a duty. Examples are Yoko, Petra and Alicia. And did we mention that these characters are pretty handy with their guns?
Most characters voiced by Nozomu Sasaki end up creepy or evil or both. These include characters like Tetsuo (and his very obvious ExpyK9999), Mello, Olba Frost, Enishi Yukishiro, and the worst of them all... Johan Liebert. The only exception is Yuusuke Urameshi, but that's just ONE breakout role compared to his whole lot of... that type of character.
Sasaki himself is probably another good example of someone who switched typecasts — he used to play a lot of sweet-voiced young boys and now does more creepy evil types. There were even rumors in Japan that he'd had some kind of surgery or injections to alter his voice. In Legend of the Galactic Heroes, which was made over a period of several years, try comparing Julian's voice at the beginning and end of the series to hear the 'change' (although arguably this could just be an example of acting, as the character had grown and matured).
Need a Tsundere Idol? Try Sakura Nogawa, often her roles will interlace with something idol related, famous roles includes Tsundere Tsubomi from Strawberry Panic!, Shiho from My-HiME and being one of Gust (Creator of the Atelier Series) newest talent to rely on. She has been cast in every Ar tonelico series so far.
Ami Koshimizu may have versatile voice styles, but she often has a consistent fanservice and humorously ecchi feeling to her roles that she plays. Kallen Stadtfeld and Ryuuko Matoi are prime examples of this.
Kenichi Suzumura plays a lot characters whom knows or have the worst luck examples are Strawberry 100% and Gundam SEED Destiny, don't feel bad though, at least the VA gets to be quite close with Hitomi Nabatame... His characters also tend to be very loud, childish or rude and scream a lot (think Shinn Asuka in SEED Destiny or Chika Akatsuki in Zombie Loan)
Hiro Shimono most notable typecast as a lead is seen as a somewhat meek person with a good sense of artist touch within him. His characters are usually pretty good at art or something culturally creative. Ayato Kamina is one such example.
Hiroaki Hirata has lamented that, after ten years building a reputation as anime's "pirate seiyuu," (Sanji, Benny, Balthier, Captain Jack Sparrow, etc.), it took exactly one role (Kotetsu T. Kaburagi from Tiger & Bunny) for him to lose this title and instead become known as the "oyaji seiyuu."
Chiaki Takahashi is mostly known for her roles as Ms. Fanservice (occasionally overlapping with Cool Big Sis) or the one who is considered sexiest on the cast, considering she is a gravure idol. However, in a subversion, the personalities of her characters could differ from ditzy (Azusa), kind and nurturing, if conflicted (Litchi), utterly flirtatious (Haineko), and... well a lot more, but they always held the 'Sexy' part well.
Issei Futamata's most common roles tend to fall along two types. One usual type would be him being cast as squeaky-voiced nerdsand/orgenerally unlucky young men (that may or may not also be a bit unstable). The other common typecasting involves him voicing random mooks and corrupt businessmen, or other villains just as sleazy.