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

向きに成る[mukininaru] to become serious
持て成し[motenashi] entertainment
成吉思汗[jingisukan] Japanese mutton and vegetable dish
亜成層圏[aseisouken] substratosphere
成す[nasu] to build up

成手[narite] candidate
育成栽培[ikuseisaibai] vegetable and fruit growing
一気呵成[ikkikasei] finishing writing, work, etc. at a stroke (stretch)
化成[kasei] change
化成工業[kaseikougyou] chemical industry