• the gravy train

• keep it for a rainy day

• down the drain

• strangely enough

• brainwave

• brain drain

• on the brain

• keep a tight rein

• rain cats and dogs

• it never rains but it pours

• keep a tight rein on it

• stranger to it

• take it with a grain of salt

• as right as rain

• rain or shine

• strange bird

• rack one's brains

• save it for a rainy day

• go against the grain

• strange to say

• pick someone's brains

• be a stranger to it

• give free rein to it