My former employer is telling me that I have to wait a year to cash out my 401k. What leverage can I use to expedite their activities relative to getting my money?

Talk to the plan administor, ot the former work place.

Did they give a reason for the year delay? How long were you employed and contributing to this 401(k), and what is the plan invested in?

Plans have a fairly wide latitude in customizing paln provisions but still staying within the law. You need to talk to the plan admin and get a reason that is backed up by the plan's rules.

But why do you want to cash out? Why not roll it over into an IRA or a new plan?