What kind of Ira do I open for bigger refund? Traditional or Roth? Or 401K?

A traditional IRA can still be opened and funded for 2016, and potentially increase your refund. 

A Roth IRA can still be opened and funded for 2016, but would not impact your refund.

A traditional 401k has the same impact as a traditional IRA, but are administered by employers, so that's not an option for 2016.