"You're about as useful as a one-legged man at an arse kicking contest"

This quote is a humorous way of saying that someone is not very useful. It implies that the person is so useless that they would not be able to contribute anything to a situation, even if it was something as simple as an arse kicking contest. The quote is also a way of highlighting the absurdity of the situation, as a one-legged man would obviously not be able to participate in such a contest. The quote is also a way of mocking the person being referred to, as it implies that they are so useless that they are not even as useful as a one-legged man. The quote is a humorous way of expressing the speaker's opinion that the person being referred to is not very useful.