no holds barred
mod. without restriction. (There is no affirmative version of this.)I want you to get that contract. Do anything—no holds barred.Try anything that will work, no holds barred.
rat hole
n. a bottomless pit. (Typically with throw and down as in the examples.)Why do they keep throwing money down that rat hole?That rat hole will absorb as much money as they can supply.The transportation system is beyond help. Giving it more subsidies is just throwing money down a rat hole.
sky's the limit
phr. “there is no upper limit.” (Always with the.)I can afford it. The sky's the limit.You can do anything you set your mind to, Billy. The sky's the limit.