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

ペンキ塗り立て[penkinuritate] wet paint
粟立つ[awadatsu] to have gooseflesh (cold or horror)
安心立命[anshinritsumei] spiritual peace and enlightenment
一頭立て[ittoudate] one-horse (carriage)
一本立ち[ippondachi] independence

引立つ[hikitatsu] to become active
隠し立て[kakushidate] secrecy
永世中立[eiseichuuritsu] permanent neutrality
永世中立国[eiseichuuritsukoku] permanent neutral country
推し立てる[oshitateru] to set up

データの先頭[deetanosentou] beginning of data
一頭[ittou] one large animal (horses, cattle, etc.)
一頭立て[ittoudate] one-horse (carriage)
咽頭[intou] pharynx
駅頭[ekitou] station

音頭[ondo] leading a group of people
会頭[kaitou] society president
街頭[gaitou] in the street
核弾頭[kakudantou] nuclear warhead
巻頭[kantou] opening page of book