Recently (and my new obsession) I've been pairing Hibiki, Mami, and Makoto up. I'm planning on using those three for iDOLM@STER Platinum Stars. Their varying vocal ranges sound nice together.
Though I haven't thought of a good unit name for them yet. Ended up naming them - Iku! Iku! Aisuru!/行く!行く!愛する! (Go! Go! Love!)
Now let's see my other units:
kotori (little birds) - Chihaya, Takane, Ritsuko
TripleM - Makoto, Miki, and Mami
Tsuki Ohimesama/月お姫様 (Moon Princesses) - Takane and Yukiho
Spicy Sugar - Hibiki, Iori, and Yayoi
BoomChickaPop! - Ami (boom), Miki (chicka), and Haruka (pop)
Midori Papuru Hoshi/緑パープル星 (Green Purple Stars) - Ritsuko, Azusa, and Miki
monoCHROME - Makoto and Yukiho
Shimai/姉妹 (Sisters) - Yayoi and Chihaya
Aoi GIRLS/青いGIRLS (Blue GIRLS) - Hibiki, Yukiho, and Chihaya
Symphony♪ - Chihaya, Takane, and Azusa
Banzai! - Hibiki and Makoto
Yutaka Girls ☆/豊かGirls ☆ (Rich Girls ☆) - Iori and Takane
TWO♥Cute♥ - Miki and Ami
ChiKaRa (Strength) - Chihaya and Haruka
daybreak - Takane and Hibiki
bIG N' Small - Azusa and Chihaya
new style - Ritsuko, Hibiki, and Yukiho
Itadakimasu!/いただきます! - Miki and Takane
contrast - Hibiki and Chihaya
Ya Genzō/や原三 (And the Original Three) - Yayoi, Yukiho, and Azusa
LoliPops - Yukiho, Mami, Iori, Yayoi, and Ami
Sweet♪Rock - Yayoi and Takane
— (pronounced dash) - Yayoi, Makoto, Haruka, Yukiho, and Miki
Kurohomura/黒炎 (Black Flame) - Takane, Makoto, and Chihaya
Ohimechin and Amami/お姫ちんと奄美 - Takane, Mami, and Ami
A-Step - Azusa and Hibiki
diamond - Takane and Azusa
Maizō/埋蔵 (Treasure Trove) - Ami, Hibiki, Takane
2inkle (pronounced Twinkle) - Iori and Yayoi
Wata Kashi/綿菓子 (Cotton Candy) - Ritsuko, Yayoi, Haruka
Valkyrie (バルキリー) - Hibiki, Takane, Chihaya
Illumination (イルミネーション) - Azusa, Yayoi, Takane
Oto no Kigou/音の記号 (Symbol of Sound) - Makoto, Takane, Yayoi
Kiku/菊 (Chrysanthemum) - Haruka, Iori, Takane
Bi no Tatsujin/美の達人 (Beauty Masters) - Iori, Chihaya, Takane
Eien no Ai/永遠の愛 (Everlasting Love) - Makoto, Hibiki, Takane
Start Line! - Mami, Hibiki, Makoto, Takane, Chihaya
...and I'll probably make more of them. ^_^
ML/CG units:Tsuki Seishin/月精神 (Moon Spirits) - Anna, Mami, Takane
Tsuki no Usagi/月のウサギ (Moon Rabbits) - Anna, Iori
Suimin-sai/睡眠祭 (Sleeping Festival) - Kozue, Anzu
BEAT! - Julia, Ayumu, Makoto
Destiny✩ - Emily, Azusa, Sayoko
Soyokaze/微風 (Gentle Breeze) - Kotoha, Fuka, Tsubasa
Disbanded:MikiBiki - Miki and Hibiki