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

御呪い[omajinai] good luck charm
呪い[noroi] curse
呪い[majinai] charm
呪う[norou] to curse
呪禁[jugon] vanquishing monsters, spirits, etc. with charms

呪術[jujutsu] magic
呪縛[jubaku] curse
呪文[jumon] spell
呪物[jubutsu] fetish
呪物崇拝[jubutsusuuhai] fetishism