The cliche that needs to go away is adding the word "much" to the end of a question. For example, the most common occurrence is it's pairing with the word jealous. Instead of just saying, "are you jealous?" the hipster doofus who is trying to be cool will instead say, "jealous much?" Not only is this remarkably stupid to begin with, it quickly became over used and passe. To the best of my knowledge, it's use has yet to incite a severe beating or even a solitary punch in the face, but it's certainly deserved. So do the world a favor and stop it.
Being the generous kind of guy I am, I will not take away one cliche without replacing it with something else. And so I offer what I consider to be a vastly under used saying: Crossing the Rubicon. It is so under used in fact that I don't think it can even be considered a cliche, rather simply a saying. It simply means passing the point of no return and it's etymology comes from Rome. When Julius Caesar, at the time a mere general, led his troops across the Rubicon River he was effectively declaring war on Rome since the river was one of the boundaries of the city and Roman law forbade this act as being treason. So in crossing the Rubicon, Caesar was announcing his intent to seize power from the senate and could no longer change his mind without facing execution. He had passed the point of no return.
Now some of you may be thinking that I'm simply being pompous by suggesting a somewhat arcane idiom, but truth be told I first learned about it many years ago when I first heard the Journey song Rubicon and had to go look it up to learn it's meaning, and I was just reminded of it today when I learned of a new show on AMC titled Rubicon. So for those of you who claim that television and rock music have no intrinsic value, put that in your pipe and smoke it.