"What do you want?" or "Can I help you?" — a curt way to ask if someone needs something.
玄関先で知らない人にいきなり「何か用？」と聞かれた。
A stranger at the door suddenly asked me, "What do you want?"
上司に呼ばれて行くと、机の前で「何か用ですか」と短く言われた。
When I went to see my boss I was asked briefly, "Do you need something?"
通りでぶつかった人に「何か用？」と言われて、驚いた。
When I bumped into someone on the street they said, "What do you want?", and I was surprised.
友達がぼんやりしているときに、冗談めかして「何か用？」とからかった。
I teased my friend jokingly with "Need something?" when they were spacing out.