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

御猪口[ochoko] small cup
片口鰯[katakuchiiwashi] Japanese anchovy (Engraulis japonica)
白口[shiroguchi] white croaker (Pennahia argentata)
悪たれ口[akutareguchi] abuse
悪口雑言[akkouzougon] all kinds of malicious gossip

異口同音[ikudouon] in concert
異口同音に[ikudouonni] in one voice
ひと口[hitokuchi] mouthful
一口商い[hitokuchiakinai] an immediate definite deal
一口同音[ikkudouon] reading in unison

御目出度う御座います[omedetougozaimasu] congratulations
駄目になる[dameninaru] to spoil
繋ぎ目[tsunagime] joint
軽目焼[karumeyaki] hard caramelized sugar candy
駄目押し[dameoshi] making doubly sure

一つ目[hitotsume] one-eyed
一合目[ichigoume] the start of a climb up a hill
一丁目[icchoume] Block 1
ひと目[ichimoku] (a) glance
一目惚れ[hitomebore] to be taken with someone at first sight (similar to "love at first sight", but not as strong)