I no longer work for Walmart and I'm having trouble getting my 2015 w2 form... what is the best and fastest way for obtaining it?

I believe Walmart issues the W-2 by posting it on a secure section of their website. If you all WalMart payroll, they will probably give you access to download your W-2.

By logging into their Website and downloading it. When you left you should have been given info on how to log in as a former employee. If not, contact the HR dept for the instructions.