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

悪足掻き[waruagaki] useless resistance
一挙手一投足[ikkyoshuittousoku] slight effort
一足[issoku] pair (footwear)
一足[hitoashi] step
一足先[hitoashisaki] one step ahead

一足飛び[issokutobi] (at) one bound
逸足[issoku] fast runner
右足[migiashi] right foot
運動不足[undoubusoku] insufficient exercise
栄養不足[eiyoubusoku] malnutrition