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

伊達男[dateotoko] dandy
一男[ichinan] boy
下女下男[gejogenan] servants
下男[genan] manservant
寡男[yamoo] widower

間男[maotoko] married woman's secret lover
既婚男性[kikondansei] married man
貴男[anata] you (referring to someone of equal or lower status)
男気[otokogi] chivalrous spirit
好男子[koudanshi] handsome man