一も二も無く[ichimonimonaku] unhesitatingly
一言二言[hitokotofutakoto] a word or two
一石二鳥[issekinichou] killing two birds with one stone
一二に及ばず[ichininioyobazu] right away
一姫二太郎[ichihimenitarou] It's good to have a girl first and then a boy

うり二つ[urifutatsu] as alike as two melons (two peas in a pod)
黄道十二宮[koudoujuunikyuu] twelve signs of the zodiac
二度[futatabi] again
最小二乗法[saishounijouhou] least-squares method
三十二分音符[sanjuunibuonpu] 32nd note

パイプ役[paipuyaku] mediator
悪役[akuyaku] villain
一役[ichiyaku] an office
一役[hitoyaku] role (which someone or something plays in a given situation)
下役[shitayaku] underling

仮役[kariyaku] temporary post
加役[kayaku] temporary extra work
監査役[kansayaku] auditor
顔役[kaoyaku] influential man
区役所[kuyakusho] ward office