There are a few things - using dark energy to explain the accelerating expansion of the universe when we really have no idea what this dark energy really might be, or dark matter to explain the missing mass that our current understanding insists should be there but that we can't find. But then Newtonian physics was everything until relativity came along and maybe it will be proven that relativity isn't quite right.
First person to scientifically prove general relativity is wrong will probably get a Nobel prize for it.
;-)
Mick