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

暗君[ankun] foolish ruler
我が君[wagakimi] my lord
君子[kunshi] man of virtue
君子豹変[kunshihyouhen] the wise readily adapt themselves to changed circumstances

君主[kunshu] ruler
君臣[kunshin] ruler and ruled
君たち[kimitachi] (used colloquially by young females) you (plural)
君臨[kunrin] reigning