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

御神酒[omiki] sacred wine or sake
ギリシア神話[girishiashinwa] Greek mythology
悪神[akujin] evil god
圧神[asshin] pressure sensation
安神[anshin] relief

伊勢大神宮[isedaijinguu] the Grand Shrines of Ise
一神教[isshinkyou] monotheism
一神論[isshinron] monotheism
運動神経[undoushinkei] motor nerves
疫病神[yakubyougami] jinx (lit: god of pestilence)