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

扠置く[sateoku] to set aside
に置いて[nioite] in
にして置く[nishiteoku] to leave as
安置[anchi] enshrinement
位置合わせ[ichiawase] alignment

位置揃え[ichisoroe] justification
位置づけ[ichitsuke] placement
一つ置き[hitotsuoki] alternate
一つ置きに[hitotsuokini] alternately
一日置き[ichinichioki] every other day