A hackneyed phrase, found in many horror/Science fiction movies. Usually spoken in low, measured tones by a villian, when approached by a smaller, supposedly weaker opponent. It is a veiled threat, which implies that any action by this ill advised smaller person will result in serious harm.

In this manner:

I wouldn't try that _pause if I were you.

These words are said with a mix of annoyance and menace. Almost as if the speaker of these words would rather not be "bothered" with the pending attack. The attitude is dismissive and not a little bit perturbed- imagine a German sheperd bothered by a Dachshund.

Oh please, run along.