ちょっと一杯[chottoippai] let's have a quick drink
ばつ一[batsuichi] being once divorced
一向[hitaburu] nothing but
サラダ一皿[saradahitosara] plate of salad

安全第一[anzendaiichi] safety first
一か八か[ichikabachika] sink or swim
一っ走り[hitoppashiri] spin (as in 'take a car for a spin')
一つ一つ[hitotsuhitotsu] one-by-one

一粒[hitotsubu] (a) grain
一粒子既約[ichiryuushikiyaku] one particle irreducible (physics)
一粒種[hitotsubudane] an only child
雨粒[amatsubu] raindrop
穀粒[kokuryuu] kernel

素粒子[soryuushi] elementary particle
素粒子加速器[soryuushikasokuki] particle accelerator
大粒[ootsubu] large grain
長粒米[chouryuumai] long grain rice
麦粒腫[bakuryuushu] sty (on the eyelid)