I'll get back to you on that one
A total cop-out used when someone is too scared to answer you and just hopes you'll disappear.
'I'll get back to you on that one' when you asked why they didn't show up to the party.
'I'll get back to you on that one' after you called their mom a llama.
'I'll get back to you on that one' when you asked if they had a brain.'