凭

píng - on the basis of, lean against, rely on

There's no particular reason to pick this word today, but I came across it when writing my 子 entry for 冲动 a couple of days ago, and it looked like a handy little word. It was in the phrase 凭一时冲动, meaning 'on the basis of an impulse'. It looks like a useful little grammatical word like 为 or 对.

他凭直觉认为她说的是谎话。
He had a hunch that she was lying.